I will be disappointed if Qui-Gon makes an appearance in this movie.
I don’t believe for a second that any potential appearance he’d make would ruin the film. But once, just for once, I want to watch a post-OT SW film and say to myself “It’s canon”. I want to see Rogue One and consider it “real” – as real to me as SW & TESB are real to me. Tossing Qui-Gon/Padme/any similar PT character in the mix will make that impossible.