Note: Regardless of what i think, it is going to happen, but here we go. First, i am going to talk about how the fight should be, later on why i preferred it over having another confrontation (or more) than what we see in A New Hope.

Dream sequence/Vision: This should happen after Obi Wan learns that Vader/Anakin is still alive, it could be done similar to how it happened in the EU (the cantina). Afterwards, at night, Obi Wan dreamed again about his duel in Mustafar against Vader, how he left him there to die. But this time, something different happens, and its a creepy and scarry Anakin Skywalker, full burned with a few implants fighting him. Its just on Obi Wan head at this point, as he does not know how Vader looks like, and from what he heard, and the last look that he gave Vader on Mustafar he will probably get that image of him on this dream. In the fight, Obi Wan will be defeated, dialogue from the past can be played as well, but before Vader finishes him Obi Wan wakes up.

Now why i do not want to see them fighting for real: First mostly of the idea of Obi Wan knowing how Vader looks, it changes the momentum of ANH, of surprised and then afterwards, being so easily defeated that at first didnt expect Vader to be so strong. Second, as the dialog of A New Hope says, it makes more impactful the duel on Mustafar, and it drives Vader even more to finally get his revenge on the movie rather than before. Third, with the possibility of changing something done by the creator himself, i am not sure on what GL thinks about this, i feel that the way it was done is enough, and its not need to have another (or more) "real" duel between these two.

This is just what i think, it can possibly be done in a great way, but i am cautious optimistic about it. Let me know what do you think down below.

Link from the vid: