The main problem of the PT was, that it left many things to the "EU", so keypoints were explained there instead in the movies ...

So the main goal should be:

A) remove things that are not explained onscreen and don't need to be shown either

B) try to make unexplained things, like "force ghosts" or "Sith" (or any other interesting keyfeature) more accessable

Lucas did himself and us in general a bad service in introducing concepts like "midichlorians" (I don't have a problem with that), but not using it further to explain why NO Jedi/Sith are cloned (THAT would have been the MAIN reason WHY, imho!) - the worst "explanation" was the "rule of two"...