If this turns out to be the case then I think Joss Whedon would be a very bold choice. Im familiar with his work and if there is one thing I know he can handle and that is ensomble casts.
Kudos to Marvel though for really thinking outside the box for directors. All their choices so far have not been obvious ones but they all seem to bring something from previous works that somehow connects to their marvel movie.
"I pledge allegiance to the hip hop"