powerful women, such as princesses, did often get to remarry. so if we hypothetically make a widowed trait or something, it wouldnt be too immersion breaking to assign it to only landless and non-heir women. it is, i feel, quite immersion breaking, however, to see consorts and even empresses remarrying, which would be absolutely beyond the pale.Not sure that's something we'll consider, as it'll complicate gameplay if you end up playing as a female ruler or get a female heir.
I tried to create an elective government before. the problem is that the succession system ignored all of the dynastic mechanics. the family of the previous ruler became the courtiers of the new one and got assigned either subpar marriages or no marriage at all. i wonder if there's a way to fix this. maybe if we count counties as private estates that are inheritable, and duchies and above as elective government posts. that way, if a family no longer control a government post, they still have their county to fall back on. not sure what this means for claims though.The regular bishopric succession isn't moddable and isn't supposed to be playable, so I doubt it can be used. It might be possible to do something with custom elective laws, but we'd then have to invent it from scratch, we'd have to figure out how it should be applied and under which circumstances it should be possible to get out of it (as it neither should be trivial nor impossible), and we'd have to figure out how to keep it from causing a game over on a frequent basis and how to keep it from making realms ludicrously stable because there's no way for vassals to consolidate power.
as for the realm being too stable, id say that would be more accurate since the main problem facing most bureaucratic rulers wasnt so much constant regional instability but rather having one employee getting too powerful. to offset realm stability, maybe severely reduce the number of vassal limit and the set the number of holding to 1, forcing the emperor to consolidate the realm. as a vassal, the key thing in elective succession is to get along with the other people. if you play the game well enough, the chance of social mobility is actually even higher than in feudal succession.