That Cena would get over with all the fans, even ones that like to root for heels.

Letting him do that would get him major heat in every town. I've seen it work when Lance Hoyt and Jimmy Rave were doing it with the Rock N Rave Infection in TNA. TNA dropped the ball because I thought that was getting them over.
After R-Truth fighting just about only other faces during the Raw Rumble last week, it looks like they were heading for a heel turn but they have to make people care about him as a face before they turn him. He's popular but only one step above Mark Henry as a name brand jobber.