I don't think there is much difference between priest and bishop in that regard. They're both indigenuous to western christianity. Only that we're used to calling officials of other religions "priests" but that's obviously as questionable as calling them bishops.
I don't want to see people titled as Priest of X in game anyway. Why not use the titles created by every religion itself? I'd rather prefer to see Archdruids, Augurs, Luminaries and Tidespeakers instead.
