After making a religion and preaching to nobles I have been quite surprised with the amount of them that consider IC religion to be "for sheep", them not to be interested in religious matters, them don't having time for such petty concerns or even having higher ideals sufficing, like monarchy, duty to the realm or war. This I did not expect, since all my characters, in SMA islands or not, are highly superstitious, and after the initial period in which they know the religions available they end up joining one. It seems natural to me that a medieval character will seek a church, if not for genuine interest in the religion then for social motives (he wants to appear as a respectable community member), plain superstition (insurance against bad luck/damnation/stuff), duty (the religion represents authority and tradition) or whatever other motive.
We could force the players to have a more pro-religious attitude in their characters, or convert their peasants and force the different-religion-peasants penalties, but I sincerely think the carrot is both more effective and more fun than the stick. So I propose we give some incentives for nobles to become part of religions:
* Morale faith bonus to troops.
* Morale/Loyalty/Control bonus to regions depending on the % of followers of the lord's religion, not applied to paganism. Added effect per temple (and temple size). Let's bring the opium of the masses!
* Ability of the priest to raise the morale of troops. This should only be unavailable to noble unit commanders of misguided or evil religions, since in the medieval times the characters should be superstitious enough to believe in the blessings from almost any holy man (and simply fear the curses of unholy men).
Any other ideas?