Lord__Vader said:
Well in answer to your question I put together a small video, it was done very very roughly and I'm sure someone as skilled as Adywan could make it way better.
It's a nice try on few frames, but doing the whole sequence would be another task. Jabba needs to look at Han in the eyes (not always maybe, but sometimes at least), plus his movements needs to match the scene, plus the lips synch, plus in the end of the scene he turns his back to the camera and I don't think we have good footage of that in ROTJ.
All in all I'd say I doubt it could be done that way. Or at least it would not be easy, even for someone like Adywan.
I guess making a new CG Jabba would be even easier! (not that I want that scene back, just answering the question)