Please excuse me. I've had another random thought:
How about replacing all the Sidious holograms with Darth Maul holograms in The Phantom Menace? In this way, you'd be able to give Maul some new dialogue, have him appear to be the primary antagonist of the film (as he was set up to be, judging by the promotional material) and actually give him a character.
It'd also make the film a stronger stand-alone piece like A New Hope, because rather than leave the mystery of who the real Dark Lord is hanging, we'd assume that he's been defeated and his scheme failed.
Also, I feel the invasion sequences of Naboo needs to be made more ominous. Currently, the lighting is very cheery (at best neutral) daylight.
Mock-up:
