[GS] Brave New World for Civ 6

[acluewithout]

We need Brave New World for Civ 6.

BNW in Civ 5 was critical to making that game a success. It added late game mechanics like Ideology and World Congress, that moved the early game from being about squabbling city states, to a late game about Global Hegemons, International Conflicts and Word Wars.

Civ 6 needs the same thing. The late game is dull and lacks conflict, there are key mechanics from Civ 5 that the game is still missing, and there are existing mechanics from RnF and GS that still need more work.

Brave New World for Civ 6 could be a Third Expansion, or could maybe just be covered by one or two smaller DLCs. I don't mind either way. But Civ 6 really needs the equivilent of Brave New World for the game to feel complete, and go from "excellent" to "best Civ / 4X ever".

Here's what I think the game needs specifically.

• Make Tier 3 and Tier 4 Governments more game changing. Tier 3 and Tier 4 Governments should be game changing, rather than just being incremental expansions on T1 and 2 Governments, so that getting to these modern “ideological” governments is a real turning point in the game. T3 and T4 Governments already have unique policy cards that can only be used with certain governments exclusive. That could be expanded, so that each T3 and 4 Government also gives you access (ie lets you build) unique military and civilian units, unique buildings and unique wonders. Additionally, I’d like see T3 and T4 Governments made more important via ideological pressure and unlocking mid and late game governors (see below).
  
  
• Ideological Pressure. BNW introduced Ideological Pressure, which used Tourism to cause happiness / amenities in neighourboring Civs to be reduced if you had differing ideologies. Civ 6 needs an equilevelent to Idelogical Pressure, which ties together Tourism, Amenities and Loyalty, which in turn creates more tension around what Tier 3 and 4 Goverments you pick and generates more global conflicts. You could have Tier 4 Governments exert additional Ideological Pressure, which would help buff those Governments, and also maybe introduce some negatives to switching Government types so that forcing someone to switch from say Democracy to Communism because of Ideological Pressure becomes a tough choice.You could also obviously have World Congress Resolutions which focus Ideologies and buffs to Alliances for shared Ideologies. As part of introducing Idelogical Pressure, I think FXS also need to tweak Amenities and Maintenance Costs generally, to create a bit more empire management challenges in the late game, and then add some Ideology related Wonders like the Pentagon, Prora etc. [Ideological Pressure is still no where to be seen post NFP, but April 2021 update has linked Tourism and Loyalty. Not quite the same thing, but at least it’s something ?]

• Late Game Governors. Governors are essentially the Civ 6 version of Civ 5's Social Policies (e.g. Victor=Honour, Magnus=Liberty, Liang=Tradition, Moshka=Piety, Reyna=Commerce, Amani=Patronage, and Pingala=Rationalism). That's cool, but what's missing is mid to late game Governors that sort of mirror Civ 5's Ideologies. It would be pretty easy to implement too - just have certain Governors unlock with the Tier 3 and 4 Government Civics. You could have new Governors unlock that focus on Colonial Cities (i.e. a Colonial Governor) and more "Idelogical" Governors that focus on Ideological Pressure, the World Congress, Spies and or that can be placed in other Civs (a bit like Ibrahim). One advantage to this is that it'd make Governors more dynamic, because they wouldn't all be available at the start, and not everyone would unlock the same Governors. It would also allow Governors to overlap a bit more, so instead of having e.g. just one "Science" Governor (Pingala) or one "Ambassador" Governer (Amani), you could get a second Govenor that overlaps a little with those, so you could potentially have more that one "Science City" or more than one Governor in various City States.
  
  
• Expanded Gov Plaza, Gov Buildings and National Wonders. National Wonders that can only be built next to your Gov Plaza or Capital. Add the ability to building Town Halls and Courts in other Cities to improve loyalty and or resist ideological pressure and or reduce maintenance costs. [Looks like the Diplomatic Quarter sort of covers this one, which is great news. I really hope we get a rebalance of World Congress Resolutions and Spies (see below) and I hope we get another Purple District in due course.]
  
  
• Vassals and Colonies. Option to hold Cities as Vassal Cities or as Colonies, rather than just holding them outright. You have less control over the City (eg, can’t building anything in the production queue) and they are more vulnerable to Spies, but you get other benefits like increased Diplo Favour, yields etc. based on how loyal the Vassal or Colony is. You can also place late game Governors in these Cities with various effects and there are specific policies for these types of Cities.

• More Economy and Trade Nodes. Overhaul of maintenance and global happiness, so that managing late game empires is harder. Perhaps also have a slider, a bit like adjusting disaster intensity, so people can increase or decrease how hard maintenance is. Also, rework Banks and Stock Markets to make them more interesting than just more flat gold.

• Future Tech. Future Tech feels very underwhelming - there's only one Future Tech unit which is the GDR; and the Future Techs themselves are underwhelming because they largely only boost the GDR (except for that one tech which "boosts" normal units by removing their CO2 cost). Future Tech needs to have more impact, by introducing more future units (and future buildings) and having Future Techs boost other units, buildings etc. FXS should also bring across the orbital layer from Beyond Earth.

• Overhaul Religion. The current Religion system is pretty cool and works very well. But it could use another pass post the base game. Specifically, I think the beliefs need a balance pass like we had with Pantheons, Apostle Promotions need expansion, Religious Buildings need a significant buff, and Religious Beliefs should unlock more unique units (not just Monks). I think there’s also a good case for letting people continue to recruit Great Prophets, with GPs acting more like Great Generals for Religious Units and being the mechanism for Evangelising Religion and Starting Inquisitions rather than using Apostles. [June 2020 made some good changes to Religion, but I still think there’s a lot more that could be done to make Religion more interesting. In particular, more unique Religious Units unlocked through Beliefs (like the Monk), more Beliefs that impact Loyalty, and maybe the return of Reformation Beliefs from Civ V.]

• Overhaul World Congress. I know Civ 6's World Congress has copped some flack, but I do think it works really well. But I also think it still needs another pass to really get it right. First, the existing resolutions need another balance pass - a particular issue is that some resolutions just have too many options for the B vote, and some just don't feel like they have much impact at all. Second, the World Congress needs more WC related Wonders, like the Apostolic Palace and the UN Building. These Wonders shouldn't just give you bonuses, but should instead unlock new available resolutions and or emergencies from the World Congress.

• Ambassadors. Bring back being able to send Spies out as Ambassadors. That would then give Spies three options or "roles", ie Spy, Counter-Spy and Ambassador, and also give everyone a bit more to do with Spies. Ambassadors could have their own missions, focused on diplomatic visibility, buffing spies, enhancing alliances and improving trade routes. And speaking of Spies...
  
  
• Overhaul Spies. Spies are another great mechanic that just need another balance pass. Specifically, I think the number of Spy Missions needs to be reduced (get rid of Recruit Partisans - it's just another reason not to build Neighourhoods - and combine Listening Post and Gain Sources), and some of the Promotions should be consolidated (e.g. combine Siphon Funds and Steal Great Works Promotion, and combine Disrupt Rocketry, Breach Dam and Pilage Industrial Zone Promotions). There should also be one or two Great People or Wonders that increase Spy Capacity, just so there's a bit more variation in how many Spies each Civ can have. [Secret Societies DLC seems to cover this somewhat, given you can get more spies through one of the societies and the societies themselves sort of add a degree of intrigue. Good stuff.] [UPDATE: really, Spies are now worse that ever given we can no longer place Spies in Ally Cities. Really stupid change. I really hope FXS revisit Spies and this change in particular. Spying on Allies is completely historical, as is taking covert actions against Allies, and in terms of gameplay there needs to be a way for “Allies” to keep messing with each other even if War has been taken off the table.]

• Industrial Zone and other Buildings. Give the IZ additional T1 Building Options (eg Stone Masons, Forge), buff Workshop (eg +1 Housing) and add a non- power related T3 Building (eg a Tech Hub that buffs production and science). Add in some missing buildings, like Courts and Townhalls (see above), Hospitals, Public Schools.
  
  
• Barbarians and City States. Give City States Unique Units, that you could use if you levy the City State, and create additional Diplo Options for City States beyond just Declare War and Levy. Give Barbarians more unique units. Also create Barb Cities that work a bit like City States (now called Free Cities). Free Cities replace Military City States and are what other Cities turn into when they loyalty flip. Envoys provide additional production for military units, and Suzerain provides additional great people. If you Loyalty flip the city, you gain back half of the envoys you put into the City. [Can’t believe FXS basically did this. Barb Mode is really just brilliant. I still think Barbs could use a few more unique units, eg Axe Men, but honestly Barbs are just 1000% better now. Awesome.]

• Units and Wonders. Add Composite Bowmen, Trebuchet, Medieval Melee (please not “Longswordsmen”, instead maybe “Man at Arms” or “Halberdman”), more Future Units (and make Future Tech more useful generally). Make Aircraft Carriers work like the GDR, ie can’t form Amardas etc or earn XP / promotions, but gain bonuses / upgrades via tech tree. Generally rebalance units (particularly anti-cav and Tanks v Mech Infantry). Add Statue of Zesus and Ideological Wonders like Prora and Pentagon. Also add Apolostolic Palace and UN Building that give you additional Diplo Favour for World Congress and unlock new resolutions and emergencies / scored competitions. [Im happy with the unit changes and new units. Very happy we got Men-at-Arms not Longswordsmen. Tanks v Mech Infantry still seems a bit messed up though.]

Sorry, I know I’ve posted about some of this stuff before. But I thought I’d put it down in one place just one last time.

I don’t know what FXS are going to do with Civ 6, and I guess we’re going to find out at some point. But the more I think about it, the more I think the game is still missing “something”, and I think that something is basically what Civ 5’s Brave New World introduced into that game and that game’s overall focus on improving diplomacy, conflict and the late game.

Guess we’ll see what happens.

[edit. Clarity and a few additional ideas.]

 

[Sostratus]

One advantage to this is that it'd make Governors my dynamic, because they wouldn't all be available at the start, and not everyone would unlock the same Governors.

which ties together Tourism, Amenities and Loyalty, which in turn creates more tension around what Tier 3 and 4 Goverments you pick and generates more global conflicts.

If we put these two together, perhaps they could have/add governors that unlock with government tiers. And some part (or all) of their promo tree can vary based on which one you picked. It can be the same dude even, just give him different hats- like the 3 guys on the BNW box art. So perhaps if we rearrange the existin gones a little, perhaps you have 5 to start with, who can be balanced around early game effectiveness; 1 each at tier 1 and 2 governments (as an example, liang could come at tier 1 and be tweaked to reflect that.) Then we add a new guy for tier 3 which helps your ideological pressure + some flavored benefits, and then perhaps a t4 governor that does, something. However, restrict the player to only being able to hire (say) 7 governors total, so you cannot pick everyone every game. And then obviously add a wonder that lets you have an extra governor pick. Some slight adjustments to the governor screen and you would be good to go.

Review Spies. Spies are another great mechanic that just need another balance pass. Specifically, I think the number of Spy Missions needs to be reduced (get rid of Recruit Partisans - it's just another reason not to build Neighourhoods - and combine Listening Post and Gain Sources), and some of the Promotions should be consolidated (e.g. combine Siphon Funds and Steal Great Works Promotion, and combine Disrupt Rocketry, Breach Dam and Pilage Industrial Zone Promotions). There should also be one or two Great People that increase Spy Capacity, just so there's a bit more variation in how many Spies each Civ can have

I think spies would be way better in general if the UI for them was through a screen where we could manage them all at once, rather than as quasi units on the map. Just something to further streamline the clicking it takes to get them assigned and help me coordinate a grand espionage strategy rather than my piecemeal methods I have now.

GPS acting like Great Generals for Religious Units and being the mechanism for Evangelising Religion and Starting Inquisitions rather than using Apostles.

If they had unique bonuses on retirement or use in some way, like other GPs, that would go a long way to spicing up the religious victory, which is currently pretty repetitive.

 

[acluewithout]

If we put these two together, perhaps they could have/add governors that unlock with government tiers. And some part (or all) of their promo tree can vary based on which one you picked. It can be the same dude even, just give him different hats- like the 3 guys on the BNW box art. So perhaps if we rearrange the existin gones a little, perhaps you have 5 to start with, who can be balanced around early game effectiveness; 1 each at tier 1 and 2 governments (as an example, liang could come at tier 1 and be tweaked to reflect that.) Then we add a new guy for tier 3 which helps your ideological pressure + some flavored benefits, and then perhaps a t4 governor that does, something. However, restrict the player to only being able to hire (say) 7 governors total, so you cannot pick everyone every game. And then obviously add a wonder that lets you have an extra governor pick. Some slight adjustments to the governor screen and you would be good to go.


I think spies would be way better in general if the UI for them was through a screen where we could manage them all at once, rather than as quasi units on the map. Just something to further streamline the clicking it takes to get them assigned and help me coordinate a grand espionage strategy rather than my piecemeal methods I have now.


If they had unique bonuses on retirement or use in some way, like other GPs, that would go a long way to spicing up the religious victory, which is currently pretty repetitive.

Yup. Agree with all that. Particularly the point about the Spy UI. Spies are Super confusing to use well in the game right now, particularly once you have a few moving about.

Of everything I’ve suggested, I think the most critical are ideological pressure, unlocking mid and late game Governors (if only to get away from having the same governors being available every single game), and just fleshing out the Future Tech and Future Units a bit more.

I’m reasonably hopeful FXS might go in that direction, even if they go with DLC instead of a full Third Expansion, and I really, really think they should. It’s the gap around those three things which is where I think 80% of that feeling that Civ 6 isn’t “complete” really comes from.

As an aside, if FXS didn’t introduce mechanics for Governors to unlock mid and late game via Civics and or Governments, I think that would create a ripe area for modders.

Cross fingers.

 

[mdl5000]

I agree with pretty much all of this. Civ 6 just isn't where Civ 5 was at this point.

- ideological pressure was important in Civ 5 because it was an overall component of a cultural victory. so was religion. now we have a "religious victory", sure, but that is simply addressed by having you generating an exorbitant amount of faith to purchase the dozens and dozens of missionaries needed to do it.

-I like the concept of governors, I just wish some of their higher tier policies have an effect on multiple cities. maybe make them incompatible with other governor policies. similar to different ideologies in Civ 5. right now you can just move them around from city to city to work on some special project (buy districts with faith, or gold, built certain improvements) and then move them again and repeat.

-I do like diplomatic favor in the world congress; I just wish there were more interesting things to vote on. Some of those votes in Civ 5 could really kick you in the butt, like banning luxuries and trade or reducing great person spawning.

-future tech could be up to anyone's imagination, but if you want more units, the giant death robot would have to be weakened. maybe make it only effective in open terrain (it's not like something that big ought to be able to move through woods or jungle easily)

-spies have become better. I just wish there were fewer but more interesting missions. stop it with the recruit partisans! I find that mechanic obnoxious. It's almost as bad as Civ 4 where spies were basically invisible bombers that blow up your improvements. That's not fun at all.

 

[nauberry]

You have very solid ideas there. I think with loyalty is just missing a more combined effect from tourism, culture and amenities to really work well. The ideological pressure could make it even more exiting than just the dark age/ golden age changes we have at the moment. It would be very cool to see loyalty struggles in larger border cities. I think cities with low loyalty should also start spawning rebel units instead of the recuit partisan spy mission. Then the reduced loyalty spy mission could be used to speed up the process if needed.

 

[acluewithout]

Added:

• Ambassadors. Bring back being able to send Spies out as Ambassadors. That would give Spies three options or "roles" then, Spy, Counter-Spy and Ambassador, and also give everyone a bit more to do with Spies. Ambassadors could have their own missions, focused on diplomatic visibility, buffing spies, enhancing alliances and improving trade routes. And speaking of Spies...

 

[acluewithout]

Added:

• Expanded Gov Plaza, Gov Buildings and National Wonders. National Wonders that can only be built next to your Gov Plaza or Capital. Add the ability to building Town Halls and Courts in other Cities to improve loyalty and or resist ideological pressure and or reduce maintenance costs.
  
  
• Vassals and Colonies. Option to hold Cities as Vassal Cities or as Colonies, rather than just holding them outright. You have less control over the City (eg, can’t building anything in the production queue) and they are more vulnerable to Spies, but you get other benefits like increased Diplo Favour, yields etc. based on how loyal the Vassal or Colony is. You can also place late game Governors in these Cities with various effects and there are specific policies for these types of Cities.

• More economy and Trade Nodes. Overhaul of maintenance and global happiness, so that managing late game empires is harder. Perhaps also have a slider, a bit like adjusting disaster intensity, so people can increase or decrease how hard maintenance is. Also add “Trade Nodes”. These are created by founding a Trading Company in a City. You can only have one Trade Node per Continent. International Trade Routes automatically route through Trade Nodes and provide benefits to Civ that controls the Trade Node (and yes, if you don’t manage to found a node, you have the option of capturing a City with a Trade Node). Also, rework Banks and Stock Markets to make them more interesting than just more flat gold.

• Industrial Zone and other Buildings. Give the IZ additional T1 Building Options (eg Stone Masons, Forge), buff Workshop (eg +1 Housing) and add a non- power related T3 Building (eg a Tech Hub that buffs production and science). Add in some missing buildings, like Courts and Townhalls (see above), Hospitals, Public Schools.

• Barbarians and City States. Give City States Unique Units, that you could use if you levy the City State, and create additional Diplo Options for City States beyond just Declare War and Levy. Give Barbarians more unique units. Also create Barb Cities that work a bit like City States (now called Free Cities). Free Cities replace Military City States and are what other Cities turn into when they loyalty flip. Envoys provide additional production for military units, and Suzerain provides additional great people. If you Loyalty flip the city, you gain back half of the envoys you put into the City.

• Units and Wonders. Add Composite Bowmen, Trebuchet, Medieval Melee (please not “Longswordsmen”, instead maybe “Man at Arms” or “Halberdman”), more Future Units (and make Future Tech more useful generally). Make Aircraft Carriers work like the GDR, ie can’t form Amardas etc or earn XP / promotions, but gain bonuses / upgrades via tech tree. Generally rebalance units (particularly anti-cav and Tanks v Mech Infantry). Add Statue of Zesus and Ideological Wonders like Prora and Pentagon. Also add Apolostolic Palace and UN Building that give you additional Diplo Favour for World Congress and unlock new resolutions and emergencies / scored competitons.

 

[Birdism]

I agree with all your ideas, particularly about the need for ideological pressure which would tie different game mechanics together nicely.
World Congress could use a rework as there are too many possible outcomes within one resolution that it feels like everyone is voting in their own corner on something different, unless by chance multiple civs coincidentally pick the same option.
Trade Nodes / Trading companies is a great new idea that I would love to see implemented that could tie into a new economic victory. The ability to found a company could somehow be related to resources (either having diversity or multiple copies of same one - not sure what would be more interesting)
Overall you offered great insights! Hope Firaxis read your post!

 

[Lazy sweeper]

Road mechanic is screwed. One good recovery point to the road to excellent would be to give every single unit the build road ability.

Barbarian options to sedentary, calm, or outrageous, would be nice.

Set aggression levels for AI would be great, not just difficulty settings..

Allow sea level rise up to the hills would be cool. Not just 3.5 mt.

Vanishing resources would be excellent.

Trade nodes based on what? If you played Europa universalis, trade nodes are outside cities, sometime in the middle of the sea....
You place your merchant in that node to steer trade power, indipendently from who owns the city....
The mechanic is totally different from CIV VI... a nice idea but I can't possibly imagine it implemented.

 

[bene_legionary]

Trade nodes based on what? If you played Europa universalis, trade nodes are outside cities, sometime in the middle of the sea....
You place your merchant in that node to steer trade power, indipendently from who owns the city....
The mechanic is totally different from CIV VI... a nice idea but I can't possibly imagine it implemented.

Random New World but Civ?

yes please, I never thought I had ever needed this in my life
Also none of the nodes are in the middle of the sea as far as I know, most offshore ones are just coastal cities.

 

[Lazy sweeper]

Random New World but Civ?

yes please, I never thought I had ever needed this in my life
Also none of the nodes are in the middle of the sea as far as I know, most offshore ones are just coastal cities.

I don't know a lot about marine power.
I could be wrong, but the strait of Hormutz, for example, is one massive trade node in the middle of the sea.
Yes it is close to Iran, Dubai, Saudi Arabia, but still contended... so why not?

Of course a GP economic power that is water based, with a floating on water economic district where one could place him, maybe host other economic GP by diplo means....
could extend tha land power to the waters without breaking the base core?

 

[bene_legionary]

Well in EU4 (btw set in 1444, no Saudi Arabia, only Nejd) Strait of Hormuz is right next to the island of Hormuz between Iran and the Arabian peninsula. It has to go to another node first before going to Iran. Arabia has only one trade node, Aden. Europe has a lot more contested spots.

Anyways, if mechanics like EU4's were to be placed into Civ it should be dependant on terrain features; e.g. oases amd rivers, or straits, river deltas and capes. It might be hard for the game to find those locations though...

 

[acluewithout]

Updated OP based on July DLC and other updates.

Interesting that Secret Societies tweaks Governors a little. Hopefully FXS will be encouraged to do a bit more with Governors in later DLC as well.

 

[The Civs 6]

Well in EU4 (btw set in 1444, no Saudi Arabia, only Nejd) Strait of Hormuz is right next to the island of Hormuz between Iran and the Arabian peninsula. It has to go to another node first before going to Iran. Arabia has only one trade node, Aden. Europe has a lot more contested spots.

Anyways, if mechanics like EU4's were to be placed into Civ it should be dependant on terrain features; e.g. oases amd rivers, or straits, river deltas and capes. It might be hard for the game to find those locations though...

On this topic, I think it's seriously worth considering whether, instead of changing the game itself, we should author maps that are intentionally designed to interact with the game's systems.

 

[AsH2]

Updated OP based on July DLC and other updates.

Interesting that Secret Societies tweaks Governors a little. Hopefully FXS will be encouraged to do a bit more with Governors in later DLC as well.

Most likely not in NFP - would be a bit counter-productive to poke around several times in same systems..

“I'm most excited that we have the ability to update the game frequently,” Amanda Bonacorso, lead producer for the New Frontier pass, told GameDaily. “Our designers are always looking at balance within the game, and since Civilization VI has so many overlapping systems, we're always trying to keep it interesting to play.”
..
“For us as developers, live service means an ongoing commitment to keep the game alive through new material and through continued updates to the base game--things that prevent the game from settling into an established pattern of play,” Bonacorso explained. “For us, this year is very much about our team learning how to treat Civilization VI as that live service game: putting out new material, seeing how our fans react, and trying new ideas.”

from GameDaily.biz Firaxis Games on Civilization VI's New Frontier pass, and keeping the game fresh four years on

 

[acluewithout]

@AsH2 Thanks for the reference. Super interesting.

Yeah, I don’t really have great hopes for any expansion to Governors in NFP, but here’s hoping.

 

[AsH2]

@AsH2 Thanks for the reference. Super interesting.

You're welcome. I was actually looking for (a text of) the source where Ed or Anton explained why they decided to flesh out new content as NFP instead of full expansion, but this was all I got.. I recall they found developing standalone game modes more appealing than a bunch of mechanics in a final pack.

Yeah, I don’t really have great hopes for any expansion to Governors in NFP, but here’s hoping.

Though I think adding a governor or two wouldn't hurt..

 

[Revanchist]

Some of your ideas are good, but I never agreed with the following around Civ 5. I still believe that it is far inferior to 4, and less than 6 especially with the district system and the clear, untarnished art style that made playing the game feel better than the morgue that was 5’s artstyle

My biggest hope is that city states become more influential and world congress is dynamic and not just clicking buttons. Hosting conferences and putting more emphasis on city individuality would put it closer to Civilization 4

 

[acluewithout]

@Revanchist Thanks for the feedback and Glad you liked some of the ideas.

To be clear, I’m not saying Civ 5 is better than 4. Instead, I’m saying Civ 5 was vastly improved by an expansion (ie BNW) which focused on the end game particularly around Ideologies and conflict, and that Civ 6 would benefit from something along the same lines. That said, much if he stuff I’m suggesting wasn’t strictly in BNW, but I think most of it used that expansion thematically or as a jumping off point.

There’s also stuff from Civ IV I’d like to see carried across, but that’s a conversation for another day.

 

[fossar_]

I agree for sure that the late game is significantly less interesting than the early game and think your idea of ideological pressure is great, there's clearly a variety of ways it could be implemented though and some would have to be thought out well. With the introduction of Secret societies the idea of additional pressure on Govenor titles through more late-game govs seems unappealing and I don't think particualrly necessary. I think it's just an issue of making the promotions relevant to different stages of the game (something Pingala in particular represents very well).

I think one great way to implement Ideology in Civ6 would be have some emergency style events where losing government types get 'sactions' where they lose gold and production or something like that with points being eared through loyalty/ideology pressure and tourism on opposing Civs and some special projects being available. There could be various world congress votes included too. I think both loyalty and ideology pressure at the same time would be overly confusing, maybe a T3 gov unlokced project to switch between the two would be on theme or it simply changes for the world at Modern Era I'd guess. International boundaries are mostly settled and times change to diplomatic penalties rather than land disputes.

The idea of vassal cities sounds just like having city states in the game. These seem to be getting a rework with the Ethiopia update so we'll see what comes from that. In general though, I'm guessing you're thinking something like puppeted cities from Civ5? Regardless your suggestions fit somewhere between that and city states, both of which are almost always worse than owning a city. I'd have to hear more about how these would work to be pursuaded as I can't see them having much impact in any game other that maps with far fewer players than the map size should have.

Late-game empire management is tedious enough as it is we really don't need more mirco-decisions and for the people who play multiplayer with turn timers it would be even more of a problem.

In total agreement that the late-game techs and civics need to be about more than units and GDR upgrades. I'm pretty sure there are new wonders coming as the Frontier Pass rolls out, hopefully the majority of them are later game things. That said, unless their production costs are kept reasonable, since they're not around very long before the game ends they have to be pretty game changing like Amundsen-Scott Station to be worth it.

I'm very keen on the idea of spies being used as Ambassadors, maybe some missions to boost tourism, sabotage enemy allicances / boost your own. It would only make sense that you would need the new diplo district to build them and probably a special mission to re-train spies into ambassador or the other way round as the promotion trees would conflict. I don't think spies need really any changing as they are though.

While there some changes you could make like giving the workshop a housing, the other buildings you refer to are only missing if you try and import Civ5 into Civ6 which doesn't make sense cos they're wildly different games. You've got the Uranium power plant for the sciency industrial building and food market to replace hospital for some of the examples you've given. The idea of including some situationally good buildings in districts seems fun but would look out of place unless the idea was also implemented for other districts too which could end up just being clumsy and/or overpowered based on spawn location. My idea of districts is that they normalise the playing field because everyone has access to the same stuff regardless of their land, this kind of thing would undermine that somewhat.

What you're describing re: barb cities is nothing novel in essence. Just making militaristic states actively aggressive, removing their individuality, and getting rid of the existing free city mechanic. None of this helps the game imo.

On the last point adding more steps to the unit upgrade path is a bad idea, if the upgrades occur too frequently then it makes timing pushes more difficult and if the defender can hold out for a short-medium while then they'll probably get to upgrade their units and overrun attackers before they can bring down the walls with old un-upgraded units. This would be especially apparent at online speed. Where it can take an era to build a sizeable army and get it to your enemy.

All in all, ideologies, ambassadors and more interesting late game please for sure but I'm not convinced yet of your other suggestions.