You're asking two separate questions. One question is who does WWE want. The other is who would I want if I ran WWE.
Who would I want? The list starts with Joe. Joe vs Punk, Joe vs Bryan. Reason enough. AJ would be alright, but he's not quite Joe's caliber. I'd loved to have the Guns in the tag team division, but that ship sailed. Roode and Storm are interesting, but I think they'd be about where Barrett is on the roster at best.
Then of course, you have the group WWE would actually like:
Sting: Doesn't need to be discussed further.
Angle: Part time, former WWE champion, a final run makes sense (provided he gets his crap together).
Hogan: Already in the new game, a legends deal makes sense. Wouldn't discount one final mania appearance/match.
Hardy: If he's clean, a part time schedule makes sense. The machine makes him relevant.
Other than that, there isn't anyone WWE would really want or need. Sure TNA has some solid hands, but WWE is loaded with solid hands. WWE feeds off of stars and getting any combination of those guys back under contract means more money for WWE (if off nothing else but the DVD's they could make of them). AJ, Roode, Storm, Aries, Joe, no matter how talented they are, they wouldn't really affect WWE's bottom line that much and at the end of the day, money is what matters.