If I recall, Illusion's Artificial Girl 2 has a semi-hidden map area behind the waterfall in the forest path area behind your house with a small church room and a prison cell, meant to be sort of an bdsm setting. I can't recall though if they had a nun outfit to go with it though, but I wouldn't doubt it. Unfortunately you can't change the guy's outfit without modding though. If you were determined enough to figure out how to replace his outfit and came up with the mesh/textures for it, it would definitely be possible to get him looking like a priest. Probably more work than you're looking for though.
If you don't mind 2D games, there are several I found with a quick search that may be of interest to you:
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