Actually, I had no objections to everybody forming a pantheon and winning immediately. It's a happy ending for everyone involved, after all
It'd be nice to see decently sized pantheons (10+ pretenders), but I guess that'd need a lot of players before it became viable - well over 20 or something like that.
I don't think there's anything to stop a player being a part of two or more pantheons, providing they're devious enough.
A hard cap of some sort might be okay - 25% of total player numbers? Or maybe 50%, even.
I'd like to encourage things towards a certain fluidity in organisation, with people changing sides when they get a better offer or rebelling against their own side to gain advancement.