But the awesome revolt armies would be my biggest beef with the game.
Yep. That's a good one. But ZPG takes care of that What I would've done is this: any occupying army that gets tossed out of a city or town suffers losses according to city or town size; the larger the city, the higher the losses up to half your army size. The resulting enemy garrison would be composed of militia-type troops, with some regulars thrown in (how many regulars depends on the amount of time you occupied). A general might be possible in a very large city. Militia troops would be vanilla with no upgrades, any regulars or general present might have an experience chevron or two, but no armor/weapon upgrades.

time would be six months per turn with all build times, aging, etc changed to reflect this
Actually, three months per turn is even better. Essentially the Shogun system of four seasons, with income paid only at fall harvest. That system added an additional layer of strategy because you had to plan your infrastructure builds and troop recruitment much more carefully. You also had to keep a reserve for bringing damaged units back to full strength. There were many times I had to field an understrength army for lack of retraining funds. Lesson learned the hard way

and the Roman civil war would happen when one played non-Romans too.
That would've been fun and interesting. Having an alliance with one Roman faction, while fighting another.