Ok, here is a recompiled list, slightly more organized.
Will Be:
Forced diplomacy, with the option of at start of scenario only, or all way through game
AI triggers
Will Not Be:
The ability to add eras.
Be able to spilt your territory into regions. A good way would be to simply select one city, the city(/ies) closest to it and say they make up a new region. A box pops up asking for the region name. Simple.
The ability to add new culture groups.
Units:
AI properly using units with less than all the worker actions selected.
AI knowing when to Upgrade and Rejoin units
The AI should stop patrolling. The number of times I've seen AI units moving back and forwards to and from the same tiles...it's ridiculous and causes a huge drain on system resources.
The ability to set whether or not a transport unit can itself be loaded onto other transports (like helicopters onto carriers). I imagine you'd need 2 load flags, then.
A box, similar to the Ignore Move Cost box, which would give a combat bonus to the unit when fighting to or from that terrain.
Ground units should be able to use air missions w/o doing weird things like flak units flying through the air on intercept missions. Although, I think this probably involves a change to the format of the INI file, with dedicated lines for intercept, recon, etc.
Be able to set whether or not a specific fast unit will retreat on a percentage chance, or will always retreat.
Make the movement cost change unit to unit. 0 meaning : the unit cannot enter this kind of terrain (-> add a list of terrain in the unit tab, where you can select the cost). To allow us to mod faster, the terrain will have a default cost, and new unit will use it, except if specifically changed. Of course, some units must have the possibility to go in land and water (to make real helicopters).
Introduce the notion of "unit class" (for instance Infantry, Cavalry, Armor, Air, Naval, Sub). Each units belongs to one of this class, and has bonuses against other class. exemple : Pikes have a bonus against the Cavalry class (but not the armor class!), Aegis Cruiser have a bonus against Air class, Destroyer against the Sub class, AT gun against Armor and MG against Infantry, etc.... The bonus could be attack and/or defense
Make the sentry function work if the fortify is disabled.
Variable unit upkeep costs, on a unit-by-unit basis
Allow Government specific units
An 'obsolete' flag for units
Allow Improvement prerequisites for units. You need a shipyard to build ships!
Make the efficiency at military police (to reduce rebellion, or prevent disorder) unit specific, so Special Forces may have a bonus for instance.
Add a new flag "affect units only" for unit, so we can make for instance chemical weapons that damage units / population, but not the building.
Add a Naval Task Force that would work as armies, but for fleet.
Add a flag "can bombard land" and "can bombard sea". So submarine can try to use their torpedo against naval transports, but cannot use it against troops on the shore. Even better, make two row : bombard strength, ROF and range against land unit / against sea unit. This way, we could have aircraft specifically designed to attack ships, other for ground attack. While they are at it, they could even make the bombard change with the class (bombard against infantry, cavalry, armor, naval, sub).
Add a flag to make aircraft loadable on carrier without the need to use to many tricks
Add a flag to tell if a unit can capture a city or not
Add a flag for unit, so it could appear "automatically" it the city is capture (good old guerilla resistors of CivIII)
Add a flag and field to limit and set the number of tiles a land unit can move from a friendly city -- and have an improvement flag which then eliminates the limit.
Make fast units able to retreat from slower fast units. For example, Cavalry with movement of 4 could retreat from Knights with movement of 3
A "Can retreat flag", becuase speed is not the only thing that should allow a unit to withdraw from combat, Think of submarines, if they could retreat, they might actualy be worth building. This would also be good for Reconisance units or special forces.
Give ships the potential for the retreat ability
Allow marines to attack other ships, and capture prizes - just like real maritime warfare!
Editor
The diplomacy text should be restructured so that it isn't reliant on knowing how many civs there are. That way you wouldn't need to mess about with that horrible string text when you add a new civ.
The units tab of the editor should have sections for inputting pedia text and pathnames for pedia icons, but being able to do so in plain English w/o worrying about stuff like PRTO, # or ^. In fact, that should probably go for all the tabs. If that takes up too much space, then a button with a pop-up asking you to type the stuff in.
Being able to move units, techs, buildings, etc. up and down the list would be handy since that affects it's position on the in-game build list.
Give modding control over movement bonus on railroads.
Add inside the editor the possibility to copy a unit or a building or a government, keeping all its attributes, so we can easily make improved version without to make everything by hand.
In the editor, sort the dropdown list , so we can easily find the prerequisite! (In my mod with 300 techs, it starts to be quite boring to do this).
Worker Jobs:
For terrain improvement, add a flag to state if they consume the worker or not.
Put back the second level of irrigation (and perhaps introduce a second level of mine as well), to give workers something to do in the end of the game.
Governments:
Add some efficiency rating for the government (science / happiness / Trade, etc) that could affect the speed at which buildings (that are commercial, religious) are created, or the production of science, gold and shields, etc.
Improvements:
Make building upgradable, for a cost that would be smaller to the regular cost. Still with my shipyard idea : Ancient shipyard can be used to create galleys. To make battleship you need a modern shipyard. In a new city, you can directly create the modern shipyard, or you can upgrade the ancient one for a lower cost. Also, ancient shipyard are removed from the build queue once modern shipyard are available.
Allow obsolete improvements and small wonders
Open up all possible features for improvements, wonders, and minor wonders -- so that, e.g., improvements might expire, and a minor wonder can place an improvement in every city.
Improvements/wonders flags and options:
- "Increases food in land" +1 food in all land tiles already producing food.
- "Increases corruption" Self-explainatory
- "Succeptible to propaganda" Self-explainatory
- "Increases war-weariness"
- "Replaces all improvements with this flag checked #2" A one or two more of this flag, please. There's more things than just power plants that could benefit from this flag.
- "Elite ground units" Self-explainatory
- Negative production. Ability to set improvement or wonder to reduce production.
Miscellaneous:
The ability to choose which tile improvements and city improvements are era-specific.
Civ-specific advisors.
The game engine should automatically draw the lines between techs. Yep, you heard me correctly; that way we don't have to mess about with the pcx files and can just add techs with the editor.
A land Transport AI strategy flag would be nice (and obviously the AI be able to use it ).
Civ-specific tech-trees.
Increase the number of levels for city (more than 3 levels), so we could have more than 2 buildings which the flag
Introduce the notion of "Internal name" and "displayed name". This could be handy for flavour unit. For instance, we can have an US Infantry, FR Infantry, UK Infantry, GE Infantry for a WWII scenario, with different animations and stats, but they will all be displayed with one name : Infantry.
Make it possible to have civ specific animation and or icon for units, but sharing the same civilopedia entry and stats -> We had the unit once, but then we change the animation to make flavour units.
Make it possible to have AND and OR prerequisites for units and techs.
Improved the efficiency of blockade to reduce the production or prevent the passage of enemy troops and or goods.
Make it possible to have more than 2 different types of barbarian. I think we need at least one for each era (the best would be 3 per era : one slow moving but stronger, one fast moving but weaker, and one naval).
Era-specific barbarians.
Introduce religions into the game. They would work a bit like governments (so the combination of religion / government gives unique bonuses). It would also be nice if a capture city retains for a while its former religion, and if unhappiness is linked to religion difference between population and owner of the city. To go with it, add a flag for units "can convert". A unit with this flag as a % of change to convert each turn one of the citizen into the owner religion.
Get a gold bonus when a trade route goes through your territory, commercial network (the programming knows that already for such a trade would stop in case of war). Trade route would then be either the shortest one or you could (even better but for latter I guess) choose it.
The ability to build bridges across single grid costal waters would be great though it maybe vulnerable to attack but that life....but its some thing thats needed specially if they add canals & real river travel...
Be able to edit civ aggressiveness for each era. A civ might be extremely violent and merciless in the middle ages, but very peaceful and loving in modern times.
The possibility to check a mod/scenario while in the editor (check if all links , pedia , etc.etc.etc are right , so that you dont need to start the game , and load the scenario just to get an error , and then do that again for every error you get)
Unit trading
Add munits in the package, including PTW munits.
Remove upper limit of 31 civs
Add a limit to the number of units of a given type you can have at the same time, to represent some unique elite force (for instance, only 1 immortal unit for Persia!)
Resources as prerequisites can be set so as they either have to be merely connected by road (the current system) OR they also have to be inside city radius, e.g. edit civ aggressiveness for each era. A civ might be extremely violent and merciless in the middle ages, but very peaceful and loving in modern times. ethnic unit localized creation.