Correct me if I'm wrong, but isn't the main purpose of this proposed scene to work the Emperor into A New Hope? And I've heard similar ideas about trying to work Yoda in the movie as well. Okay, so, with all six of these films (and I don't really think about them as six films I-VI, but in this particular case I'll go with it) together, I admit that A New Hope does stand out as being the only movie that doesn't showcase these two characters. I won't even make my standard defense about ruining the reveal for these characters later on since we're accepting them as I-VI at the moment. But the point remains that they're not there simply because there's no reason for them to be there. They have nothing to do, and any attempt to incorporate them in would seem, in my opinion, forced. It would be the equivalent of trying to work Lando into A New Hope because it's the only movie of the original trilogy not the feature him. There would be a scene during the Death Star battle where it has Han flying away from Yavin when he suddenly gets a call from his old buddy Lando who, as it turns out, convinces Han to go back and help the Rebels. Yeah, okay, that scene sucks, but I hope my point remains the same. Forcing characters in for the sake of them being there isn't a good enough reason for them to be there. I must admit that Revenge of the Sith did a good job with that by having Jar-Jar and the other Naboo peoples stand in the background as extras during Padme's funeral. They didn't say anything and, besides Jar-Jar, were barely noticeable, and they belonged there. But there was no attempt, except with Jar-Jar, that really pointed out, "Hey, we're here! Look at us! We were in the other movies!"

So I agree with whoever said that it's a good scene from a fanfiction perspective and is cool to think about the events that transpired after Vader escaped, but they really don't belong in the actual movie.