#2 He hasn't had a real heel run yet
They call Dean Ambrose the lunatic fringe. However, he's been anything but a lunatic these past few weeks, and may even be a little sensitive on that front. This week, when he was told that he was on 'lunatic time', Ambrose stormed off in a huff, realizing that his friends saw him as a joke and little more.
The only way for Ambrose to showcase the lunatic side of his character would be to go heel. He's not had a chance to go heel since he first made his debut as a Shield member. Seth Rollins had a great heel run, when Ambrose played the top babyface.
Could Ambrose change his fortunes by going heel and potentially become the top guy once again? I can certainly see this to be the case, going forward.