I'm kind of torn on Dwayne Johnson as Luke Cage. I'm literally working through both my acceptance and reservations on this proposed casting as I type.
On one hand, someone as high-profile as The Rock being attached to a Luke Cage or even Heroes for Hire project could have a similar effect as Edgar Wright did for Ant-Man; in that, there would be very few barriers to getting the film green-lit. The Rock does ooze charisma. His performance as Roadblock in GI Joe 2 was probably the only redeeming aspect of that movie, and I actually bought him as a black character.
However, I've never actually thought of Johnson as being 'black'. Luke Cage's African American-ness (in my mind) is his defining trait. It speaks to both his anti-authoritarian stance as well as his need to do good for his community, especially to help the poor and down-trodden.
Hmm, I clearly need to give this more thought.