These should be the actors:
Scout-Casey Affleck
Soldier-Mel Gibson
Pyro-any guy since his face is never shown and speaks only in mumbles
Demoman-Seal
Heavy-Jean Claude Van Damme
Engineer-Billy Bob Thornton
Medic-Christoph Waltz
Sniper-Russel Crowe
Spy-Jean Reno
This is just my opinion, that is as long Uwe Boll stays away from this project :P