There should be an option for Vinny to grow his facial hair even longer! That man needs a long pointy goatee xD
But of the 3, I'll say Brad. I've seen Jeff with some stubble before and I don't think a full on beard would suit. As for Matt... We don't see him enough for it to be a big deal :P
@razielcuts: And longer hair perhaps. 'Chris Hemsworth as Thor' is a crucial quality I look for in production staff.
So I guess we're just down to Alexis and Rorie, huh? Also, I know Norman Chan is working elsewhere, but maybe there's room for his mirror-universe counterpart...