I would like a new expansion to add in this order:
1. Political movements, elections and different leaders
- Different organisations are active in your country. In democracies there are elections and other organisations can win causing trouble for you. This could for example change your UA or something like that. You can use different methods of surpression but it can cause unhapiness, be very costly, etc. In dictatorships there are no elections but political dissidents can still grow if you don't focus on what people want, are too repressive, etc. This should however not be cooked down to something stupid like "freedom=democracy, order & autocracy=dictatorship". All ideologies should be able to have a democratic system or a dictatorship. Some fascist movements today (at least claim to) support demcracy, some order-oriented countries like Venezuela are a lot more democratic than a lot of liberal contries (the EU Trokias occupation of Greece right now for exampe) and a lot of "freedom"-oriented countries like puppetstates of the US in Latin America, Iraq, Afghanistan, etc. can hardly be called democracies.
This would also mean the implementation of different leaders. Leaders should die and be replaced at least at every new age. And when political movements appear (don't know if they should be there from start or appear at a certain age) there should be a possiblity for a leader to be replaced through revolution or election. If there are early dissidents they could for example force a change in social policies?
Other civs should be able to use spies to increase support for other political movements in your civ. Separatists should be able to appear and make cities leave your civ if they win over you militarily or politically. The World Congress should be able to vote for support to dissidents in your empire or joint military action against a movement trying to grab power, etc.
A lot of my ideas are probably stupid or already well covered by other funtions in game. I'm just throwing out a system I would really like to have better implemented.
2. Environmental issues
The environment should be an important part of late game. Sanctions through the UN, global projects against fossile fuels and for the preservation of natural environments (a resolution that gives gold/tourism for unimproved tiles maybe?), etc. Feels like a big miss to not have this implemented better.
3. Health system
Ties in well with both the above mentioned systems as well.
4. Joint militairy actions
Already mentioned in my first category but even if that one isn't implemented I would really like to be able to coordinate militairy actions to free an occupied city state, support a civ or CS under attack, peace-resolutions through UN that can be ignored but then forces other civs to support an action against the warmongerer with troops, etc.