This could add some interesting options for the player. Here are some ideas...
The way the rules are now I believe each AP resident gets to propose 3 resolutions before there is another vote held for who gets to sit in the AP. So, if a player gets approved to have Absolute power (also note if a player has Absolute Power other members of the AP should be more inclined to vote "Yes" on resolutions he proposes) then say after 3 resolutions the AI evaluates the AP resident and if things are going well there want be a vote for a new AP resident. But if things are going bad for any of the members they may call for a revote.
If only one calls for a revote then if that vote fails to oust the AP resident then the AP resident has an option to declare war on, or excommunicate the one who called for a revote or the member could chose to renounce his AP membership.
If more than one calls for a revote the strongest one of the recallers could be pitted against the AP resident in a new vote. And depending on how the vote goes and the Members reaction it could end in a Civil War between members, the AP resident getting excommunicated, or the AP resident just retains his title, etc.
This could simulate the rise and fall of leader figures through out history, but from a religious point of veiw. Much like the emperors of the Roman Empire back in the day. So many of them became Absolute Rulers just to be ousted or assassinated by other members of the Senate. "Et tu, Brute? Then fall, Caesar! "
That would be some bit of coding but I believe it would be pretty simple once I figured it out. Right now I am adding the 3 new Force Civic options and its a pain cause the Civics work different than the other vote options but I am making progress.
by all means, do it if you can. however, i just want to point out some historical accuracy... this does indeed seem to simulate how the Roman Catholic Church was, in fact, divided. this was known as the Great
Schism. the first (east-west one) resulted in the establishment of the roman catholic church separate from the eastern orthodox. i believe there is a mod which tries to simulate this already--but i doubt it has anything to do with the AP. the mechanics you describe really doens't go against what happened in real life, so i am for it! but, ideally, any civil wars should result in the introduction of a new religion. you should look into what mod already exists to figure out what they did or you can make your own--if you plan to go that route. i wonder though if that's too complicated! but if you're game, man, i say go for it. you'll definitely get much kudos from all of us for even trying and getting something half decent. there are very few coders and very few try something as ambitious as this...
on a side note. i was thinking again about making the AP resident an absolute position by default. the historical reason stands, for sure, but i think there is a way to make it work without unbalancing the game. if you've played medieval 2: total war, you'll note that they handle the papacy quite differently can civ 4 does: in that game, the pope is AI controlled and works for no one. now, i'm not suggesting that, but there are other checks and balances that we can copy from that game:
1. the Pope can call for you to stop warring against a fellow Christian. if you don't, you can be excommunicated (and any other Christian kingdom can attack you as they please without invoking the wrath of the Papacy)
2. just keep the revote going, as already coded. a bad resident will eventually be ousted.
3. how many votes you get is based on how "pious" your kingdom is: how many religous buldings you have in addiiton to how many priests. you can simulate this in civ 4 by counting how many temples, monastaries, cathedrals, and missionaries you have of the AP's religion. (ideally, you could make a religion meter which tracks what percentage of population in each city is a particular religion, but that might get too complex)
4. joining a crusade grants papal favor. successfully completing a crusade (in that game, the pope directs the capture of a single enemy city) results in even greater favor. while favor may be too difficult to do in civ 4, you make it so that every happiness is added to all civ's cities with the AP religion--but only for civs that AREN'T the resident and only for cities weren't newly acquired in the holy war. so here is a reward for complying and not defying... which simulates the indulgences granted by the pope.
as such, the AP resident can only wield absolute power for a very short time. you can add disfavor for bad holy wars as well. this is very balanced and requires less code... and ultimately, is historically accurate. it would be difficult for any human player to abuse the AP because he still subject to a democratic vote. and if he pisses other civs off, he loses their vote. so keeping good relations is key to keeping the seat.
and when you said you a player might want to defy a resolution to build up his forces, that's fine, because you can still build up forces without having to join the Holy War. remember that the way you coded it is that it is a defensive pact and only civ actually declares Holy War--which works great b/c in history, no Pope forced anyone to go crusading, but they didn't, there would just be consequences. now, if said civ doesn't go to war and get excommunicated, remember that the AP resident may not get your votes next time, and maybe you'll be resident next time.
so, in conclusion, i think the solution that is both balanced and historically accurate is to make the AP resident choose resolutions that go into effect without a vote with each civ having an option to defy it (though not making it null). thus, as described above, if i want to force organized religion, it happens--but each individual civ is given the option to defy it for their own particular civ. if i want to sanction holy war, it happens automatically, and the mechanics remain the same as is since no one civ is forced to go to war yet. defiance results in the AP resident having the option to excommunicate any one member. but, of course, what goes around comes around...