Y'know I was thinking who else would be a good Nick Fury... Djmon Honsou, from Blood Diamond. He could be pretty intense.I mean if we go for an 'out of the box' option, he could be interesting. Or... even heh... Keifer Sutherland. I mean at least people look at him think 'Jack Bauer' well Nick Fury's about as Jack as you can get really.
RDJ has had me thinking that even if an actor isn't a 'name' they could still work out well in the role. Granted you need someone that people might know, but still you don't need an actor that's in EVERYTHING.
OR... introduce the concept of LMDs early on. If we see different guys saying 'I'm Nick Fury', we can say they're LMDs that keep the true Nick Fury secret, then when we finally get an Avengers movie, they can introduce the 'real' Nick Fury who will be the main Nick Fury, if they can lock him into a contract. That way they can always go 'Well the second Fury is the real one's actual look.' or something. So they CAN go the route with say, the black Fury, the white Fury being different guys, who knows. Just as long as they don't make it a 'Nikki Fury' and cast Angelina Jolie or something LOL