Originally Posted by metaphysician
As people have said, Planet Hulk really doesn't fit the MCU. Nobody really wants to banish the Hulk, nor have they for some time. And Banner has *more* control over the Hulk now, not less, to the point where he can actually act as a superhero under sufficiently extreme circumstances. It would really, really come off as out-of-nowhere and unjustified.
The only possible exception would be if it weren't a deliberate banishment, but an *accidental* one, resulting from a science experiment gone bad or such. Make it a bit of a planetary romance where both Banner *and* Hulk have something to do.
Doing Planet Hulk doesn't mean they have to ape the story beat-for-beat. They could easily have it so that Hulk is shot into space by an enemy, like the Leader, instead of the heroes. Or he could end up accidentally stranded in space while doing something heroic similar to how a certain somebody in a certain movie very nearly got stuck somewhere VERY far away from Earth.
Point is, how he gets to Sakaar ISN'T what matters, and is only important if you want to do World War Hulk (Which they should never do. World War Hulk sucked). The important thing is Sakaar and what the Hulk does when he gets there.