I think when it comes to adding footage from other sources, you have to be really careful of continuity when it comes to cinematography and artistic direction, that’s why fan films are nearly impossible to incorporate into fan edits, the cinematography is usually completely inconsistent with the film at hand. Some of the best alternative star wars footage is from the video games cutscenes just due to the fact that the aesthetic of star wars is usually spot on there. Take for example the light side ending of force unleashed 2, there’s a scene at the end where starkiller talks to vader on the ship, and vader is tied up. Some shots from this scene are nearly photo realistic and could easily be used to replace a bunch of the shots at the end of ROTS if you wish to avoid using footage that REMINDS the audience of cringey moments.