If WWE didn't rape his personality as a baby face (which they might very well do), he could be a good baby face, in my opinion. Aside from always having to put a new person into the Hall Of Pain, he could maintain the same persona, only he's feuding with heels rather than faces. He'd be a good enemy for The Shield, Brock Lesnar, etc. I know the latter isn't likely to happen, but it'd be fun to watch. If he and Brock crossed paths, Henry threatening to re-open the Hall Of Pain and induct his biggest inductee ever would be awesome.
That said, he's better suited as a heel. Ryback should have never turned heel and Henry shouldn't turn face. The role that Ryback is in now should have gone to Henry, in my opinion. Unless their long term plan is to have Cena transition into a feud with Henry at some point after the Ryback rivalry is done.
I personally think Henry should only turn face at the end of his career. Have him and a heel become partners in crime for a short while or something similar and then they lose a big match or something doesn't go their way and the heel slaps Henry over it (I picture this as something a manager would do but there's none around) and then Henry absolutely crushes them and the crowd pops for it loud. I'm thinking of the way Andre was slapped by Heenan at Wrestlemania 6 and Andre turned back face for the first time in years by bitch slapping Heenan and Haku (his partner) to end his career on a good note.