I honestly believe Candice Michelle needs to work on fully returning without reinjuring herself first, before they decide to repackage her and push her in another direction. Right now, Candice is VERY injury prone, and it wouldn't shock me to see her reinjure herself in her first match back. I seriously hope it doesn't happen, but it's unfortunately what she's been doing lately.
As far as her being a heel, she was a decent heel, but to be honest the fans react to her in a big way. I'm unsure if it's because of GoDaddy.com or why, but the fact is you don't really wanna take that much of a positive reaction away from someone. When she was a heel, she was barely gaining any reaction, positive or negative.
Melina is a great heel, and to be honest not a very good face. So all in all, I think Melina could return as a heel again, or at best a tweener. Somehow blaming Mickie James or Candice for her injury even. How is unknown, but I'm sure she could.