Perhaps a stupid suggestion, but why not just remove consecrated altars from most maps? They probably don't make a lot of sense (why would youu randomly find a altar to valrield buried deep within a dungeon?) I know the generic map loading code removed random consecration of altars. And I think there are altars to all the gods in the major cities or nearby, so its not like the random altars are really needed. Now I do know that the random map code does periodically insert special maps, and those may be dedicated to a specific god - I don't have a problem with that - those areas are usually well defined, so if someon accidentaly prays in one of those, they would get as much sympathy from me as if they played in a temple to another god.