Bingo: I really like the idea of Anakin/Vader being "the other". Again, I can go one way or the other with Leia being Luke's sister, though it still feels tacked on to try and top the "I am your father" bit from EMPIRE. I personally would still edit out Ben's appearance on Dagobah and end the scene with Luke looking worried with one of the segway music cues kicking in (ala along the lines of when Luke found his aunt and uncle dead) and leave it for Luke to figure out through the Force and reveal what he knows/discovers to the audience as he reveals it to Leia (not to mention, it would be more shocking to find out somewhere near the end of the second act right before everyone is about to meet their fates, than have exposition Ben lay it on the audience before the story really starts to progress).
Why Leia couldn't have "heard" Luke at the end of EMPIRE simply because they have a close bond either as possible lovers (or love interests) or just because of all the stuff they went through beforehand is beyond me.
Granted, Obi Wan would have less "face time", but is it really critical to the story that Obi Wan spells out everything for Luke/The Audience? Also keep in mind that Ben's appearances dwindle from movie to movie as Luke grows up from a kid to an adult - the main point being that in order for Luke to become a true Jedi, he has to finish his final test/confrontation ALONE without any outside help. It would also allude to the "rogue's gallery of Jedi ghosts" at the end as all variations of father figures for Luke, as they all had a hand in him growing up not just as a Jedi but as a human being (hence a good reason that they, and not Qui Jon or any other Jedi, appear in ghostly form). Yoda's and Ben's appearances SHOULD be extremely limited, as JEDI is the movie where Luke has to become an adult in the sense that when 20 and 30 year olds become parents, one of the first things they learn is self-sacrifice (be it money, time, freedom to simply be lazy or have fun). Granted, Luke does not have any children of his own, but if he is to reboot the Jedi and the Republic, he is essentially taking the mantle of being the "founding father" of the New Republic and has to prove that he won't give in to the same hate and evil his father and Palpatine gave into. Thus, when we see Anakin (as played by Sebastian Shaw), Obi Wan and Yoda, they are all giving their collective nod of approval at seeing their collective son grow up.
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On another note, isn't one of the main faults of JEDI the lack of urgency or a real threat to the main characters? Be it when Luke finds his aunt and uncle dead, or Luke is in the Falcon at the end of EMPIRE, both scenes made me feel at least like you had no idea what the character could do to escape the situation - I was genuinely worried. Other than maybe the Rancor scene, I can't say I really felt that watching JEDI.
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From an overall editing point of view, I would still start JEDI out on Tatooine, and leave the introduction of the DS2 when the Emperor arrives (where you could do the SD overshadowed by the Executor, which is then overshadowed by the DS2). The opening shot with Vader landing is pretty redundant, as we see essentially the same shot when the Emperor arrives, not to mention it "blows the wad" right off the bat by revealing the Death Star to the audience in the first shot.
I would consider changing the opening scrawl to describe the rebels suspect the Emperor has a plan to "destroy the rebellion once and for all", but do not know the details, with the second part of the scroll "with Luke finishing his training, he heads to Tatooine to rescue his long, lost friend..." (or something to that effect). The bottom line being that there is no mention of the Emperor building yet another Death Star. That way when we see it (much less if you take the Executor reveal from EMPIRE, but extend it to have the DS2 overshadow it, which leads to the Emperor departing the Executor and to the shuttle bay per the original JEDI scene), it is a definite shock.
That way the DS2 is at least something of a surprise and we see it only after the "B" story is wrapped up. I would try to eliminate as much exposition and edit around the actual facial acting the actors do (like mentioned before, rather than have Leia comment on Luke revealing to her that she is his sister, keep her quiet and only show her expression so her face and her eyes tell us how she is feeling as opposed to Carrie Fisher literally telling us).