Shame on me, I hadn't even thought of Hamill! That would be great. And there's hope, because they convinced him to do a cameo for Chuck, so I assume this is an easier sell.
I wish they would keep the Joker out of this. Even a "pre-Joker". (From interviews, etc, you know they're going to go there.) I know he has various origins, but in my mind, the Joker only exists because Batman exists.