I think the OT could benefit from some minor changes, mostly musical, to make the saga flow more as a whole. The Across the Stars theme for the Luke/Leia scene in ROTJ. A re-recorded, less-forceful version of Battle of the Heroes for the Obi-Wan/Vader duel in ANH (or maybe even just the eight-note lead in would be sufficient). And certainly the addition of the Imperial March to ANH.

ROTJ could benefit from some tightening of the Jabba's Palace sequence, and the removal of a lot of the Ewok stuff.

My opinion, however, is that the saga should be strictly viewed in order as I-VI.