What movie would be interesting to see if two of the main actors or actresses were to switch roles with one another?

I'm not a huge fan of movies that are based around superheroes; however, I enjoy them for what they are. That said, I was recently watching the trailer for Justice League and thought about how fun it would be to see Henry Cavill and Ben Affleck switch roles with one another. Cavill is far more charismatic than his role as Superman makes him out to be (just look at The Man From U.N.C.L.E.). I can see him nailing the role of a 30 something Bruce Wayne. Conversely, Affleck has the confidence/self-assured presence required to pull off a slightly older Man of Steel. I'm not saying that I would have preferred it this way...it's simply a reversal that I would have found interesting.