This sounds good. I think you could at least play around with starting the film with Kylo already on his way to Exegol. Either starting with the shot of Kylo’s ship flying to the edge of the nebula, or pan down to the nebula as Kylo jumps out of it and flies towards the surface of Exegol.

The fact that we don’t have any extra deleted scenes of Mustafar, or the fact it doesn’t even look like Mustafar, makes me lean toward just removing it and allows the film to not start on an action scene for a change.