JGL is a great actor but can he do it while wearing a mask? High profile actors tend to have trouble with hiding their face. Tobey Maguire couldn't keep his mask on as Spiderman and everybody makes fun of Tom Hardy's Bane so what do you do? I think for characters like that you have to concentrate on the actors voice not their face. Think of James Earl Jones as Darth Vader, the voice is the character.