Re: How much did Ledgers death change the ending of DK?
Eh, I think it could've been written that way if they wanted it to and it could've been a pretty satisfying cameo. I think Joker would see the humor in him of all people being a judge, giving people two rotten choices and watching them squirm, and knowing that they're all going to die anyway. I think he'd find it all deliciously ironic and pretty hilarious actually.
The only thing is you couldn't just have The Joker in a Batman film and not have him scheming to "play" with Batman somehow too, so there'd have to be more story changes. You couldn't just swap Crane for Joker, but I do think The Joker as the judge could've potentially worked for part of his hypothetical TDKR role.