I would not want to be anyone else. I might want some changes in my body, but I have no desire not to be me.
Logically, if you weren't you then YOU would not have existed or would no longer exist. If would be suicide of one's personality.
My gut feeling is that you meant if you could change lives with someone, and still be you, who would it be. There is a BIG difference than being someone else because if you were someone else then you would no longer exist.