As long as he puts someone over on the way out, would that be the worst thing?
The only real reservation that I have about Cena is that, at this stage of his wrestling career, neither wins nor losses do anything for him, but a loss to Cena could be damaging to quite a few people. At the same time, you don't want to bring Cena out to pop the live crowd, and just having him jobbing in every match, so who on the roster could afford to job to Cena, that's not currently in the title picture? Dolph and Miz, maybe AJ? But, aside from AJ, who's paying to watch that?
Don't get me wrong, there are dudes on the roster that Cena could have interesting matches with. I'd pay to watch Cena versus GUNTHER, as long as GUNTHER wins the blowoff. I don't think I've ever seen Cena work Priest before... Hell, let 'em wrestle Dom, it'd be worth it just for the interactions with Rhea.