I’m still thinking about the HRE mechanism
You said If I don’t control the electorat provinces, my heir wont become Emperor, that's a good idea. So there’s a lot possible for you to trigger events and conditions.

Here are some questions:
1. Is it possible to create a general „The pope“ (some of them acted more like generals rather than popes) situated in rome.
He will be given (deterministic but very historical) always, if an emperor dies an title “imperator romani” ancillary(?), the same that my emperor has at the beginning of the game. In order to get this title my faction heir has to go to rome physically (which may be blocked by Italian states which is very historical and thanks to your genious map already works pretty good) and exchange the title.
But maybe it’s not possible as a papal-state general because I cant exchange a title of a foreign general. Maybe one should place the pope as a general of the HRE into rome with this title. Similarly it would work with cologne and rex teutonicae title.
2. What advantages are connected to this title and to the rex teutonicae title already implemented?