The Tavern

This feels like/is an artefact from older versions. Even as someone who played a ton when sacrifices were very common, I keep forgetting to do it before autoexploring after trivial fights, and I imagine I'm not alone there. More importantly, it's a constant annoyance that doesn't require any thought (sac if you need an ally, if not, then eat if you are hungry, otherwise sac and move on).

I assume fedhas corpse sacrifice still exists because the toadstools it produces are needed for Evolution, but I don't see how a system where fedhas gives an equivalent amount of piety on kills, and praying turns corpses into toadstools and zombies into skeletons without piety gain, is any worse. I'm sure it's not an ideal fix either, and fedhas isn't fun to most players in general, but to me it seems like a simple and clear improvement.

It might be strange to make praying have this kind of unique effect, but Fedhas praying is already an exception now that it's the only corpse sacrificing prayer, and also with the weird zombie -> skeleton power.

sacrifice_before_explore = true

I hope it is default.

It is not and corpse sacrifice is an unnecessary mechanic no matter how much you improve its interface. (I only had it off because of my old auto_sacrifice = before_explore setting, I know it exists.)

Sounds good to me. Just give piety for kills that leave a corpse. The "contribution to the ecosystem" message wouldn't even have to change.