Challenges to your Empire(post victory)

One thing I noticed in RTW was once you started to get the ball rolling on your empire, there wasn't much to stop you. It is probably true that ones you have the resources you should beat other but in game, it tends to get boring or just not challenging.

What I'd like to see is a victory condition where you not only obtain x amount of provinces but also HOLD them for a certain amount of time. In a way, to consolidate your hold from enemies. Don't get me wrong, I'm not asking for a realm divide! That was the worst feature in S2. You work for endless hours to makes pacts, alliances only to get betrayed but most if not all. It's a smack to a player for the sake of challenge.

What I want is perhaps a final attack to your provinces that are neighbored by enemy factions or a civil war, rebellions, or even betrayal by a strong general. We could even have a nice attack by "barbarians" if you are playing as Rome

I'd prefer that was with death of the FL as larger Empires have a 'patriotism' level or something where basically the larger the Empire the more difficult to keep everyone feeling part of the same culture/enterprise. So with a bar similar to Shogun 2 showing the status of feeling in the Empire which rises with size, when that bar is about halfway full rebellions start to become a problem with Heirs or changes of government accompanied by rebellions which get larger the more full the bar is. Well prepared Heirs can more easily sweep rebellions aside (educated, some military experience, good authority -personal, religious, family connections, etc-).

Eventually even a well prepared Heir will face rebellion no matter what if the Empire is large enough. So this way players who play far past the campaign objectives still have rebellions to contend with when trying to 'color the map with 1 color' sort of objective in mind though they can try to race the clock and complete total conquest while their last ruler is alive not to face a massive divisive rebellion where Empire might split not only into 2 rival factions but 4-5.