Dominic, I see what you mean; of course his presence is not necessary. But you said in your earlier post that he “does not belong in this movie.” That’s a bit hyperbole, I think, and implies that his presence is damaging. I just wonder in what way you think his presence is damaging to the film.
It depends what you consider damaging. Vader’s scene is the most obvious reshoot material because he never meets the heroes face to face. It comes across as a very last minute addition (which it is). It also overturns their sacrifice by making the audience root for him instead.
I think this problem could be alleviated by having a main character stuck in that hallway with Vader. Maybe a current character could be rewritten to be in that scene, or it could be a new character. The idea is that the audience is hopeful because this character managed to avoid the destruction of Scariff, so we’re rooting for him to get out of there. Things are looking up for this character. Then the hallway scene plays out like normal, and this main character is cut down by Vader. That way the audience is conflicted, we’re rooting for the main character because we’ve spent the last 2 hours with him, but we’re also rooting for Vader, because he’s badass. The scene would carry more emotional weight than it currently does, because as it is Vader is just cutting down nameless rebels.
That being said, I still love the hallway scene. I think it totally makes sense for Vader to be there, and for him to be using his lightsaber in that way.