But that would require the game to be a simulation that actually modeled the reasons for those events. Even Paradox doesn't do that really. It is mostly lame scripting of events.
Yes it would, but you could abstract and simplify some mechanics. Also one idea from CK is good and should be used in more 4X/Total War style games: limits to the amount of provinces/cities you can rule on your own, and having to appoint vassals or governors to provinces above that limit.
That alone would already help in simulating more realistic ancient, medieval and early modern empires. Communication and travel was slow until the 19th century when railroads and telegraphs were invented, so in a large empire you can't have total centralization.
So the player will have to appoint governors or give land to vassals depending on distance to capital or on size of empire.
These governors can become corrupt and wage civil wars, etc.
And if those civil wars had mechanics that more consistently led to new rulers becoming independent, rather than the empire just going back to normal once the rebels were beaten, it would already add a lot more dynamism to the game.
There are many reasons for governors to rebel. There are just as many reasons for the population to rebel. A lot of these elements are already extant in both Paradox and Total War games. Religion, culture, etc. If you empire consists of many different nationalities, they will have a tendency to rebel. Same with religions. The Assyrian empire collapsed essentially because at some point, all the conquered peoples decided they had enough of being oppressed by brutal conquerors and rose up, and the Assyrian military couldn't handle all the pressure of the many rebellions, along with foreign powers using the opportunity to attack.
Then, just add a more dynamic stability stat, like the stability Paradox uses in the EU games except less static. Stability could be a factor of:
- how well the economy works
- how successful wars are
- whether your cities have enough food
- how much unrest there is among conquered peoples
- how multicultural and multireligious your empire is
And when you have a large empire encompassing many different cultures and religions, tensions are already high. One single lost major battle, or one major famine or plague, and everything might collapse. Cities where the majority of the population is of a different culture or religion will declare independence, governors and vassals will send armies to the capital to depose you, shit hits the fan. Suddenly you are no longer an invincible superpower, but are fighting for your life against an empire that turned against you.
The mechanics don't even have to be more complex than, say, what CK2, EU4, and Vicky2 are already doing. Except that these mechanics have more of an influence on whether your empire stays together or falls apart.