2. J. August Richards
Although J. August Richards has already played Michael Peterson in the pilot episode of Agents of S.H.I.E.L.D, it wasn't exactly a major, pivotal role in the Marvel Cinematic Universe and, since he made a good job of it, it could serve as a potential rehearsal for a bigger role. Richards played the muscle and enforcer of the group in Joss Whedon's Angel up until 2004 - his role of Charles Gunn being an incredibly popular one - so stepping up a gear to play someone like Luke Cage wouldn't be that much of a stretch. While he might not typically look like the kind of guy who would play Luke Cage (he doesn't have that rough diamond appearance), there's nothing to say that he couldn't grow a bit of facial hair and give it a go! He's certainly an outside shot, but his name has in fact been mentioned in association with the role and I for one wouldn't be against the idea.