Perhaps it would be easiest to just have it display specifically your religion for priests, and all other religions are represented by a singular common color. I mean, it's not like your religion is going to say, "They're all heathens, but these heathens we want to convert less than those heathens."
That turns this into simply a request to remove the time/gold requirement for getting a religious spread map drawn.
I'm not sure how that's any different than asking to be able to get scout reports of any region just by clicking on them.
