Luke Evans would be my choice, he has the gritty look that they're going for in the more recent Bond films.
I hope it's not Hiddlestone or Cavill, they made their auditions in Night Manager and Man From U.N.C.L.E respectively and I wasn't convinced by either. Nothing against them as actors as they've been good in other films/TV series but I think they're too polished to be Bond.