I remember I made a thread a long time ago about him reminding me of Joker, and I think he could pull off a Joker like gimmick. Just give Ambrose some rope, a mic and some TNT and lets see what he can do.
He's appeared in one promo and spoke for less than 2 minutes. Pretty hard to make the leap from that to Joker no matter how much all of the Batman fanboys want it to happen. Just let the guy's character progress organically and watch him flourish.