I've seen it referenced in quite a few different threads..but a quick search of the mod forum brings up this, which implies there also may be a limit on the number of provinces..

https://forums.totalwar.org/vb/showt...on+slot+limits

if those two things are true, it seems unlikely your grand plan could be achieved by way of a mod using the existing game engine

which is an unfortunate thing, but bear in mind I could be completely wrong