All of Anakin's scenes would have to be reshot in II and III to remove the horrible Hayden Christensen, that would be a start. But not a complete fix you would still have the horrible direction and horrible script. Ineptitude of Lucas and all involved to tell a compelling and moving human story.
Anyway there is no reason to redo them they were extremely successful business ventures as was Crystal Skull despite what fans thought of them.
Just like the sw blu ray saga set records and there is zero reason for Disney to release the originals based on sales of the already available set.
What to please a few people ? They are a business and in business to make money.
The possible Few thousand who care about film preservation or like the old versions better is not enough to undertake a major and expensive restoration.