It's one of these three.
Manu Bennett probably... I know he did a decent job as Deathstroke in Arrow, but I really liked him a Crixus in the Spartacus series on Starz. I'd want the look(hair, facial hair, etc.) to be close to what it was in Spartacus: War of the Damned... slightly longer/shoulder-length hair, full beard, etc.
I'd want him to portray William Greystoke as a refined, cultured individual with a darker, wilder side to him... definitely rugged and almost primitive/instinctive at times.
@last_arashikage: Its one of the reasons why I have faith in the American remake, he is 'training' the crew in choreography and It seems like they have a long time to adjust.
If they can turn a soap star into a believable killing machine then there should be no problems with Kitsch and Grillo.