I was thinking about how to do the alt floors and i thought about a level selection / progression like Slay the Spire or Inscryption, where you choose your path, i think that could give this game a new level of depth that would be perfect, and it would fit nicely with the Isaac theme, maybe you can put angel and devil deals in this choose your own path style gameplay ( i dont know how that way of selecting levels is called xD)
English is not my main language so sorry for all the gramatical and logical errors.