In watching through the movie, skipping around to imitate our ideas, I think the opening feels very rushed removing Mustafar and the chess scene.
I really don’t mind Mustafar as is, so this isn’t an obvious answer. It might be best as it is, even without the meat of the scene, with or without a couple establishing shots.
This movie just doesn’t give us much wiggle room.
I think I agree with you about Mustafar. The film already sorely misses huge chunks of unreleased scenes, and cutting not one but two scenes from the first ten minutes wouldn’t do any favors to its jarring, non-stop pacing.
The chess scene at the end is so good that I don’t really want to see it returned to its original spot lol. So far I’d rather fix Mustafar, unless we go the radical route and begin the film with something else and then lead up to Kylo’s journey and finding Palpatine.