I think I may put my own suggestion here too as well in regards of the late game. World wars whch are meant to be the highly dynamic events are under represented as for now so far in the main DoC mod. I don't know how can it be improved, but the way it goes now is many nations worldwide declare war on each other, barely do anything and then after some turns make peace with barely any changes on the world map. I think the world wars should be more impactful, with AI pushing to make huge advancements and territory captures. Not necessarily through the conqueror events once again, but through increasing the AI aggressiveness for the first half of XX Century to some very high levels, possibly.
Also, would've been neat to have an improvement on the civil war mechanic. I really wish it was possible for a player to actually run through civil wars and have the ability to have the civil war gameplays instead of having civil war as a total game over. I wish to be able to run through reconquering cities of my empire in a massive civil war, seeing my empire fractured, and then reunified through my efforts, even if with some losses at the end. Especially when it comes to Russian civ, which had a giant civil war in 1918-1923, one of the biggest and bloodiest in history only surpassed by the Chinese civil wars. I'd possibly propose some intense revolutionary events to be leading to a civil war, like more than one or two civics being changed at once while also mixed with instability.
For example, to form a USSR in a full-fledged way with communism, totalitarianism and more, more than one civic has to be changed. This could result in many independents to secede, representing "The Whites", that have to be recaptured. Same also for when the time comes to end with communism, changing several civics to turn Russia into a democracy, resulting in the post-communist crisis (which is, interestingly enough, represented in the main RFC mod, but not in Leoreth's), a crisis that could lead to all the previously captured civilizations (not independents), like Ukraine (Ruthenia), Turkestan (Central Asian Turks) and many other ones that may have been captured by that time, to go independent.
Or, if we speak of the other prominent civil war events with other civilizations, another example we may take is the American civil war of the XIX Century. A big civic change leading to several cities going independent in the south. Or China abandoning monarchy and switching to communism, while also undergoing through the warlord era and civil war of its own as a result of it, with several cities going independent. Not all civic changes should be leading to civil wars though, otherwise the game will have civilizations breaking up into them constantly, causing a huge mess on the map. Which is why I think it should only be applied to some major civic changes only in the late game by the most part, especially with how the majority of the modern wars after the two World Wars are the civil wars pretty much.
EDIT: Just saw the commentary above on the impossibility of including the civil war mechanic due to the timescale issues, I agree with that. Still, would've been neat to have some changes to the idea that a civil war is a game over for a human player, instead letting a player to go through reconquering land just like in the original RFC. Also the post-communist crisis from the original RFC as the remaining idea for reintroduction
