Mine would have to be Alice because she would make a great friend/sister or Esme, it would have been nice to see both of them a bit more in the films, I don't like Esme's hair in Eclipse though it looks to dark!!
Rosalie would be nice once yo got to know her, does everyone not really like her because of the way she treats Bella????
Jasper & Emmett are gorgeous, Carlisle would make a great dad, although he does look too young!!
I like Carlisle and alice other than the three main characters.