Well its a difference between bending a characters personality and playing someone completely different outright.
And exchanging personalities would imply its a personality-swap curse, and not a Nemesis curse. Which would actually.. hmm, if they swapped it to that it could be fun. I suppose it doesn't just interest me as a whole really XD; but if its optional then its fine, I don't mind if people do it. My characters can just sit and wtf at them lol