I’m actually really worried about the hints of a pre-ANH Vader vs Obi Wan rematch. Many people seem to have conveniently forgotten the line “when I left you, I was but the learner; now I am the master”. A duel between them would be the definition of breaking the canon for fan service.
That line was vague though. He didn’t say “When I left you, I was burning next to a pit of lava while screaming about how much I hate you.” There were no direct lines about what exactly their last confrontation was, so there could potentially be room for another duel in between there.
Yeah, but I just can’t imagine Vader ever describing himself as a “learner”, unless he’s talking about the time he didn’t have the suit, trying to cover for the fact he was humiliated and defeated on Mustafar. It also makes the ANH duel less powerful if they’ve met in between. I agree though that it could potentially be done well, I think if a duel would happen it would definitely be a meaningful part of the story and character development Obi will have in the show.
Also as I said, why not just go for a force vision of some kind?