I'm for Gandolfini was Bullock. That would be awesome casting.
Fergie? Hmm, I dunno. She could pass as a Latina I think.
She did have a role in Poseidon and Tarantino is using her in Grindhouse, so...
Just think about how many musicians have acted. Will Smith, Mark Wahlberg, Jennifer Hudson, David Bowie, Dwight Yoakam, Ice Cube, Flea from the Red Hot Chilli Peppers, Meat Loaf, Randy Travis- hell even Mickey Dolenz from The Beach Boys. Some of them have been very iffy(like Travis), others like Ice Cube and Flea are alright and then some like Will Smith and Mark Wahlberg have been quite good.