This is an old one, but in regards to the first pages subject of Yoda in the Prequels.. would it be possible to do Yoda akin to the Wizard in THE WIZARD OF OZ, to the degree that you never see him as the tiny muppet, but only as an imposing hologram (maybe this is where Palpatine gets his idea of communication from)? Maybe through bit players added in, it could be suggested that not only is Yoda never seen, but no one knows where he lives... that those Jedi who reach the level high enough to be trained by hm are given the "hood over the head and thrown in the car trunk" treatment, so when they come to they don't know they're on Dagobah.*
* Yes, Obi tells Luke to go to the Dagobah system in EMPIRE, but the procedures the Jedi had would have been long gone, and things being what they were, I don't think Ben had the time to beat around the bush anymore.
In regards to Tattooine in JEDI, there is nothing saying that Jabba isn't located on a different part of the planet that ISN'T a desert.. we ARE talking about an entire planet.
Same thing with the prequels. You can either call it something else other than Tattooine, or use CG and other methods to create greens and different colors (as well as other alterations to the basic and background scenery) to differentiate it with what we see in ANH.
I would consider getting rid of Jabba's scene in TPM (as in: he's not on Tattooine yet) and insert him on Geonosis, per the idea above that the events in the prequels led him to becoming a thief and a scoundrel.
I like the idea of using Prowse for the unveiled Vader scenes. His voice would have to be altered to a lower pitch (to account for Jones' voice coming out the mask), but otherwise would be a nice way of acknowledging the man who wore the suit in all 3 OT films.