10. Getting All The Actors Together
It might sound silly, but simply getting all of the massive A-list actors together for an ensemble movie (such as Civil War) which would include characters from all three current franchises would be a task in itself. Granted, the casts of each franchise are already pretty huge and consist of big name actors, but this would be a whole different ball game. Commitments to other projects have already forced changes in the franchises as they currently stand (see Zachary Levi being unable to play Fandral in the first Thor movie as an example), so getting Robert Downey Jr., Hugh Jackman, Andrew Garfield, Ian McKellen, Samuel L. Jackson, Paul Giamatti, Scarlett Johansson, Jennifer Lawrence, Patrick Stewart, Jamie Bell et al together for one project could be incredibly difficult to achieve.