For one, how has he "singe handedly" won the audience back? He's sucked energy off of Daniel Bryan and quite a bit off of Dean Ambrose, just saying.
I say personally almost any guy with the right gimmick, dance partners and set up could be world champion. That being said, Reigns' gimmick might not be perfect, but his dance partner list is pretty nice right now(Rollins, Wyatt, Sheamus, etc) and his set up is being built correctly. So I see no reason why he couldn't work as champion, but as face. I really can't say for certain. Being the face is different. You figure to be champion you just need a couple guys who could make you look good while you have the belt but to be the face, you have to be able to make everyone look good. Can Reigns do that, I think down the line he might but not at this juncture.
But let me just say, I'm not bought in on the audience forgiving him and genuinely liking the guy yet. Maybe why he's getting cheered more is because the fans are thinking WWE has pulled off on him, but the moment they think he's being forced again, let the booing commence. I mean think about what Reigns' has done since the Rumble, he beat Daniel Bryan(a great thing) but lost to Lesnar(technically he didn't lose but he surely didn't win), he beat Big Show(okay...) and has lost multiple title matches/MitB matches since. The crowd has every reason to believe the WWE is done pushing him. I mean he's feuding with Bray now who just got done feuding with Ryback, an absent Taker and Ambrose months before that.