I suppose Qui-gon appearing to confront Vader and let Obi-wan escape would be a nice moment in many respects but it would all depend on execution.
« I know who you are. I know what you want. You are looking for vengeance but I can tell you this is not the way. I do have a very particular set of skills. Skills I have acquired over a very long Jedi career. Skills that make me a nightmare for Sith people like you. If you let my former padawan go now that’ll be the end of it, Anakin. I Will not look for you anymore, I will not pursue you, but if you don’t, I will look for you, I will find you and I will kill you. »