Meneth, would you consider nerfing Antipopes? Now that the AI makes them in Vanilla they are seriously screwing the game.
A) It's way too easy to make one, and the AI seems to make them for no real reason. When starting in 867, it only takes a few years before some carolingian king makes an Antipope. In 1066, same, with either the HRE or some other kingdom.
B) When you're a vassal to a king who instituted an antipope, you immediately lose the curia mechanics. You can't stay loyal to the Pope. In fact, vassal have no choice at all. Their head of religion simply become the Antipope, and there's not even a single opinion modifier.
C) Kings who institute the Antipope cannot be excommunicated, and other rulers / vassals don't even get a CB to depose them / depose the Antipope. In fact, the only way to "destroy" an Antipope, I think, is that he becomes the official Pope by the ruler waging war on the official Pope and deposing him.
D) It's seriously screwing up Moral Authority. Starting in 867, by 876 moral authority had already dropped to 10 %. Heresies everywhere.
Imho, they should be harder to institute (AI should have a reason to do it, not just because they can). Vassals of kings who institute Antipopes should be able to choose which side they favour. Kings who make antipopes should be excommunicated (and should be seen as such by those who stay loyal to the Pope). When an Antipope dies, the king would decide whether to make a new Antipope or return to loyalty to the Pope. When the king dies, his successor would decide whether to keep the Antipope or return to loyalty to the Pope.