Quote Originally Posted by Assertn
Well, if it was that easy, then Luffy would not have been able to beat Crocodile or Enel.

Hmm, maybe; but it seems like if their weakness is exploited, and they are still conscious, then they could in theory revert to their element and restore their body. For instance, if immediately after the attack, Ace is able to turn himself into pure flames; maybe when he re-forms he will have a torso again.