First of all, this is just pure fantasy booking and is just for entertaining purposes, so chill out before ranting in the comments lol.
Second of all...I'll get this out of the way, i dont like John Cena, and i don't mean John Felix Anthony Cena, the guy, i mean John Cena, the character, i wont deny it was kind of cool back in the day when he was some kind of a bad ass, but nowadays, hes just boring and doing the same old crap most of the time.
But the way i see it, the guy has a lot of potential, the more he stays as a lame boring face, the better he could be as a heel, the way i see it, he could be a one man NWO if they wanted him to, i mean, did you see how he kicked jack swager's ass last Monday? it was kinda bad ass, and quite entertaining.
So, i've been thinking about the whole thing for a while, creating matches and bookings in my mind, and some of the things i'd do would be something like this:
Cena goes heel and decides to screw everyone in the roster, hes angry, hes pissed, he goes around kicking asses and dominating the roster to eventually get the wwe championship, then, on a live smackdown, he goes and literally forces teddy long to book him in a match for the whc and he gets it by cheating or just plain dominating, then sometime after that he goes and gets the IC, heck he could even get the US title, and even the tag team belts, just imagine, he makes a team with some random heel, they win the titles because of course they cheat in some way, and after the match, cena kicks his partner's ass and takes that belt too, now, how awesome would it be to have one guy walking around with every single belt? then i'd probably unify the IC and US titles, and maybe even the WWEC and WHC to make an undisputed title again.
Another thing i'd do would be putting him on a stable a la 4 horseman, he could get new talents to the main event like evolution did with orton and batista, i think that would be an awesome stable for a guy like lets say ziggler, maybe even swagger, ryder could go heel too, to pay the debts he has with cena for putting him over and stuff.
So, what would you guys do with a heel cena? how would you book him?