Ron Perlman because everything's better with Ron Perlman in it. Kevin Spacey because nobody does duplicitous backstabbing murdering bastard better.
WALTON. GODDAMN. GOGGINS.
I'm all in favour of all those choices (especially McDonough) but Goggins would be absolutely perfect. His performance on Justified, with his ornate speeches and flowery dialogue, makes me think he'd be more than capable of pulling off Milchs' dialogue.
Wait... The Bastard Executioner got cancelled? So, that bastard's not going to get his revenge before, obviously, dying due to an unforeseen double-cross in the name of the kingdom?
Other than that, I really got to re-watch Deadwood...