Oh, that makes more sense. As far as specific CK2Plus mechanics go to combat a powerful vassal, there isn't anything added to stop this. I would say that in Vanilla CK2, there is a plot that can be started by a vassal to force another vassal to give up a title, but that's perhaps the one specific limiting factor.
I'd think the main reason defensive pacts don't apply inside an independent realm is that 1.) Casus Belli are much harder to acquire against a fellow vassal, while an independent realms can have Holy Wars, County Conquests against their neighbors. In addition, 2.) as a powerful Duke or King under a King or Emperor, you really have all the same problems an independent ruler would have with their vassals, in addition to having a liege that could potentially revoke your titles or arrest you.
Now, for 1, I think that this makes it pretty easy to expand if you're a vassal on the edge of your liege's territory and you attack nearby independent provinces, but this WILL raise your threat level and cause defensive pacts to form.
For 2, I think some aspects of CK2Plus do work pretty well to make this more difficult if under an Imperial Government System, as your liege may revoke your Duchies or Kingdoms without consequence every time your titles are passed on.
I think the real issue you're experiencing (and I'm sure other veteran CK2 players understand as well) is that the AI simply isn't very good at managing a massive Empires or Kingdoms, and so every HRE becomes an Elective Monarchy that can never assemble a strong power base from which it can truly dominate its vassals. The "Realm Peace" feature is somewhat effective at preventing vassals from gaining power, but the AI isn't very good at using it, and so the Conclave DLC made it much easier to steal your fellow vassals' titles. (As previously, simply getting "Medium Crown Authority" stopped ALL vassal infighting).
So in short:
I don't know of any particular CK2Plus mechanics that do what you asked, but fellow vassals can use the intrigue plot to remove your titles (they ask the liege to revoke them).
The reason it's easy to expand as a vassal is that although mechanics are in place, the AI isn't very good at using them to deliberately weaken powerful vassals in their realm.
The AI is okay at being an unruly vassal, but has never gotten its commanding rulership down.
- 1
- 1
.png){kind=avatar}
