I agree with some of this specifically linking some UUs to governments, resources, religions, city states etc.> Military, CIV units are fixed to one common by era for each class (melee infantry, light cavalry, etc) and one (or rarely two) UU replacing a common one for a whole civ.
More UU for each civ, more units by class on the same era, additional units linked to districts, governments, resources and religions, customizable equipment and armament, levy and professional units, etc. All these are possible to implement into a 4X game.
I don't necessarily care for every civ having two or more UUs. For some I think it be too difficult to find for example what do the Zulu have besides the Impi, unless we go into civilian units?
I also don't necessarily care for more units of the same class every era, besides slinger into archer in Ancient. It's bad enough upgrading every era such as Warrior to Swordsman, and then to Man-At Arms, especially playing with Gaul.
I'd love it if we could change leaders every time you switch governments, but I think that's unlikely to happen. That being said I do hope that governments are even more impactful. For example if you choose to establish a Monarchy you can propose a Royal Marriage by marrying off a "noble" citizen to another civ you have an alliance with for enhanced diplomatic relationships.> Factions, inner changing politics like dynasties and parties, linked to policies and ideologies, interacting with the affinity of each city (districts). Factions and population is the more shallow, irrelevant and unrealistic part of CIV when in real history was what most leaders dedicated the more. Meanwhile in CIV minigames about collect paintings and novels have more impact and detail.
I quite like the district and building in district ideas. I don't think that most districts of the same type should be the same. I hope that for future iterations each district gets some sort of alternate buildings to choose from. For example a Commercial Hub in one city might build a market for gold, but another will have a caravanserai for adding extra trade routes.> Cities, historical buildings were not limited to fixed grouping, eras, techs, terrain, etc. They were changing alot from the new techs, ideologies, economy, enviroment and population needs. Mods for CIV games even before districs have a lot of more things to attend on your cities.
As much as I'd like this I'm not sure how this would work especially if we continue down the trend of achieving a singular goal of reaching certain milestones for a Scientific Victory. I do at leas think a culture "tree" is much easier to accomplish something similar.> Technology, the fixed paths of technologies, requirements and sequences is artificialy accommodated to an outdated vision of "western progress". Time ago was 100% possible for Firaxis to implement either alternative tech trees or a more flexible and variated common one, this is nothing difficult for a 4X game and would add a lot of flavor to civs, but we dont have even a single branch of techs exclusive for Native American, Central Asiatic, etc.