Seeing as many editors (including Ady) don't see contradiction with the EU as a problem (by definition none of the EU is seen on screen) that in of itself is not an impediment to anything ever happening in a fan edit.

The only real impediments are the effort needed to make it happen and if the change actually works within the context of the films.

Neither are impediments to it ever happening but one reduces the probability greatly and the other is subjective and dependent on how well it is accomplished.

Much of the EU is contradicted by or has to do cartwheels to reconcile itself with the films as it is.

ROTJ has many problems that go beyond the visuals and the treatment of Fett is a major one (as is the daft death of Yoda in the current cut).

In it's way it's as problematic as the prequels in terms of story so altering and shifting story points isn't as big a deal for me as doing major surgery on the story of ANH or ESB.