Have you considered extending Rey’s force vision which she gets after picking up the Lightsaber? In the novelization, it was suppose to start with Rey seeing from a distance Luke and Vader’s Bespin duel, and you can see remnants of that with the collapsing hallway in the vision which is the Bespin Cloud City Hallway. It’d be kind of interesting if you could somehow work that back in.
I don’t think adding the duel would add anything to the story that we haven’t already seen.
Rey’s Force Vision makes even less sense with the context of The Last Jedi, but I wouldn’t know where to begin in changing that. It’s probably best to wait until Episode 9 before messing with that part.