We all know why Mark Hamill is a natural choice, thing is he said Arkham City would be his last Joker voice job, so I don't think he'd want to go right to what is often viewed as a Pseudo Joker.

I love the Kefka voice in Dissida, though not entirely fond of it's Terra, I picture her more Mature sounding, I'd cast Michelle Trachtenberg.

And Lacey Chabert for Celes.

And as Cliche as it is, I feel compelled to want Christopher Lee for The Emperor.