So I started a campaign as Crown of Aragon and on turn 2 or so I'm asked by the pope to join the Albigensian Crusade and turn my back on the default ally Toulouse to help the French. Of course I heed the popes word and get thrown into a war on two fronts because the Reconquista is also going on. Apparently I'm also the only gullible fool to do so, because not even the French are at war with Toulouse.
Doesn't matter, the Reconquista goes swimmingly and I'm even making way towards Toulouse. By turn 28 I get excommunicated because of a steady downwards spiral of bad diplomatic relations with the Papal state, which drops my standing every couple of turns. Why do I have those bad relations?
1. Religious aversion... no I didn't convert to Islam, the pope just doesn't like catholics.
2. Empire size (forgot the correct name for that one)... which makes about as much sense.
I reloaded an earlier save and showered the pope with gifts, dropped all trade agreements he disliked and even gifted him Bourdeaux... still excommunicado traitoris within a couple of turns.

So in essence I did all the pope ever asked, not a thing to piss him off and still the default downwards spiral of diplomatic relations makes the campaign a dead end at roundabout turn 30.

It's a cool mod and all, but this has to be an oversight.