Spoiler warning again: Toward the end of Ragnarok, once Thor has successfully returned Bruce Banner to his human form after two long years as a gamma-powered brute, the movie makes a big deal about how if he turns again, he may not ever be able to revert back to being Bruce Banner. Needless to say, this happens about 4.3 seconds before Banner turns back into the Hulk, presumably dooming himself to a permanent life as a monster who can't keep a pair of pants intact.
But what if that's meant to set up an attempt to "cure" banner by separating him from the Hulk once and for all? It's something that's been done in the comics more than a few times, and given what happened with Tony Stark's last attempt at fixing a major problem, having that kind of experiment go tragically wrong would fit right in with the rest of the universe. From a filmmaking standpoint, there's an even bigger benefit, too: if you separate the Hulk from Bruce Banner, you actually give Mark Ruffalo something to do.
Don't get it wrong, Ruffalo's great as the Hulk, but providing the voice for a giant computer-generated monster with a limited vocabulary and exactly one emotion is a little limiting. It's when he's Banner that he really gets the chance to shine as an actor, and while the hard-hitting scenes of the Hulk smashing Loki, Thor, and anyone else who gets in his way make for some fantastic action sequences, the bits and pieces that we see of Banner as a human, struggling with his anger and solving problems with his brain rather than his fists, are an underrated part of the MCU saga.
While he serves as a two-fisted brick on the team, Hulk's entire deal as a solo character revolves around a person dealing with himself. Separating them would help to underline that, and a purely raging Hulk would certainly provide a cinematic challenge. And, just like it has in the comics, recombining the two halves could give us a Hulk with Banner's brain, something that could work as a pretty interesting change for the next phase of movies, after years of seeing the big green brute in action.