As far as I understood it from my lacking Japanese (and God forbid, I translate stuff on Danbooru orz), Remilia wanted Sakuya's leg to keep it for after Sakuya dies, and enjoy it with the first wine she made when she first came to the mansion.
Strange way to reminisce about your Perfect and Elegant Maid after her passing away.
Probably part of Sakuya's deal. She made a pledge of eternal servitude to the devil, but she always wants to die as a human. Remi doesn't like it either but Sakuya always refuse becoming immortal and Remi can't just give her that for free.
"don't you think that's a cheap price for an escape clause from a deal with the devil ?
Seriously, if that Kappa ointment from WHH could heal any injury, I wouldn't mind to have a lean juicy cut made from myself and instantly regenerated with the ointment, I too would want to taste myself. For real. But only under that specific condition, that I don't lose anything, nor get permanently scarred from it, in other words, it would be impossible! As such, I would NOT want to eat myself.
EH?And here I was, hoping to taste it...Eeh!?Can't we have it now?That's too bad...NO!Oh...And I won't give you any anyway, Flan!