I think Rob has a lot of potential, but I really would rather see Franco play my favorite vocalist--just a personal preference. The physical similarities between Franco and Buckley are great, and Franco is one of the best young actors out there today. Plus, he's about the age now that Buckley was when he died, just a little older.
BA2: Phoenix as Cash. I -really- want to see La vie en rose, though. I have high hopes for Cotillard. I'll stream it later this week before Netflix removes it.
BA3: Gainsbourg, lol. Though known for her acting. She's so...-cool-. The embodiment of French cool and sexiness.
EDIT: lol, David--that shot with the candles and "Hallelujah"--that's totally how this movie will end.
Oh, and Simone--just finished "La vie en rose," and yes. Cotillard would be my pick. She was fantastic.