Unfortunately, I'm not really sure if character swapping for superheroes can be done just yet. For example, Spider-Man. Fans would love a Miles Morales or even Ben Reilley spin off or trade off movie. Although fans love these characters, it might not really be possible yet because of the way our superhero movies have been operating. Same actor for same character for same secret identity. Change in secret identity or origin is simply too new in the cinematic universe to work. Especially with the majority of audiences including common folk who are normally going with a friend, think it might be fun, going because of the Marvel banner and not knowing much about the comics. Let me start with my quick theory on why Miles Morales might not work in the foreseeable future. Simply because he's not Peter Parker. He's quickly becoming one of my favorite characters and is almost equal with Pete for me but I don't think it could work. At least not yet. Maybe a decade down the line where more versions of the Ultimates comics might somehow make there way onto the big screen *cough* Fantastic Four *cough*.
It might also be because of the same reason we can't get a Planet Hulk movie. People don't want to see change. Audiences are used to watching quick clips of Hulk destroying something or someone, not necessarily Bruce Banner running around doing his thing. (Although I quite enjoyed Brucie's interactions in Age of Ultron, but that's just me.) If there were to be a Planet Hulk movie, audiences better expect to see Bruce for most of it because a straight up Hulk live action movie might prove to be difficult. Or audiences might have to get used to seeing Gray Hulk to compensate. Just like they would have to get used to the Black Spiderman Miles Morales. Comic lovers on the other hand, we're just biding our time.