despite all the good arguments made for having fett, i do feel it would be a distracting subplot, and kind of unnecessary, and could be viewed as a fan service (like fett in AOTC). i would only include him if you find that the restructured ROTJ creates a gap that he could fill. i wouldnt go making a gap to put him in.
using him for plot movement, or an alternative reveal to an item would be cool. just a fett episode squeezed into the running of the film would be a bit silly.