You mean like for looks, or like actually turning into that enemy during a battle?
I can get behind the transformation idea; it'd be pretty cool if we can suddenly become Shane-in-a-Power-Suit or Malistaire. As for polymorphing into enemies during combat, I'm not sure. The only use I'd see for it is gaining a ton of Health, but at the cost of worse stats in many departments and who knows how messed up your Polymorph's Deck is going to be.
