My brother and I just had a four hour car ride, and this topic came up. Basically we dished on it for the entire trip.
Here are our conclusions.
ROTJ, like the prequals, although far less egregious, suffered from a flawed execution, and not (in our opinion) fundamentally bad ideas.
Changes we would see:
JABBAS PALACE-
It is Leia, not Luke, who organizes the rescue. In fact, dialogue dictates that a while back Luke sent R2 to Leia, and no one has seen Luke in a while.
Leia's plan needs R2 in the Palace to help her deactivate the carbonite. Lando has already snuck in, 3PO and R2 hand themselves over, and Leia comes in disguise. Just like in the film she and Han (and R2) get caught.
Then Luke shows up, all mysterious. My brother and I both thought some kind of visual to cue that Luke had changed was in order. We had four ideas.
-Long hair. Akin to Anakin in ROTS.
-Short hair, like Anakin had in AOTC, minus the rattail.
-An Obi-Wan-esque cropped beard.
-Make up to show the scarring he recieved at Vader's hands healed poorly.
This change shows he's different, and hopefully makes the audience a little more likely to suspect he'll fall to the Dark Side. Also, when he flips his hood back "You will bring captain Solo and the Wookie to me" its kind of a shock.
From here on in the Jabba sequence runs more or less like in the movie with two changes.
During the skiff battle Chewie should toss some dude like a football into the Sarlac. Seriously, Chewie never gets to cut loose.
Han get's his site back a little faster, which leads to a confrontation with Boba. Boba wraps Luke in the rope, then Han yells at him and the two have an old-West shootout moment. Boba is faster, but Han ducks and falls, spinning and shooting at Boba. He misses, but it richochets, igniting Fett's jetpack and sending him to his doom. It keeps the moment similar, while giving Han a Hero Moment and killing Fett slightly more satisfactorilly.
After the Barge goes boom, the lost Sandstorm scene is inserted. It provides another set, making the film feel bigger, and gives Han and Lando a moment to acknowledge Han's forgiving him.
Luke returns to Dagobah, where it seems he's been for some time, training. He rushes back because Yoda is ill. THe scene plays the same, but when Luke asks if Vader is his father, Yoda says "Ah, the question you've never asked." implying the issue had been an elephant in the hut for some time. This way we have a reason for why Luke is suddenly so badass, he's been with Yoda all this time.
At the Rebel Briefing, it's a much more diverse crowd. The Prune-faces are featured more, as well as a more ethnically and genderwise diverse human crowd. A whole contingent of guys in differnet uniforms (something vaguely Napoleonic to stand out) are sitting together, to give the impression of diverse forces joining together for this one big rush. And Lando's copilot should be there.
Lando is only a commander... just to make it funny that Han outranks him.
Another contingent of people greet Leia. They are the surviving Alderaanians, converting their merchant vessels to warcraft for thsi attack. The leader tries to convince Leia to stay away from the battle, because 'she's all they have left.' Leia says that if they lose, none of them will have anything left. (A nice moment for Leia to show some leadership).
Otherwise the film would be mostly the same until we meet the Ewoks.
Ewoks need to be much more intense. Not scary, but not cuddly (cute is ok). They have bone-totems on their belts, and claws, and mud caked in their fur. The Ewoks have been apparently waging a guerrilla war against the Imperials the whole time. Moff Jerjerod keeps denying that there is any problem with 'the natives,' clearly indicating that there is a problem. When the gang is captured by the Ewoks, empty stormtrooper armor is piled next to the cooking fire.
When 3PO tells his story, the Ewoks pass around a horn bubbling with a noxious drink, and all the heroes drink it as an initiation (just to imply the Ewoks have some kind of culture of their own).
I wouldn't change a damn thing about the Emperor or any of the scenes of him, Vader and Luke. (except that he really needs a nicer shuttle). I think they're perfect.
ENDOR BATTLE:
No Ewok steals the speederbike. Let Chewie do it. He deserves some more action.
More Ewoks die. Not a bloodbath, but we should see some get shot. We should also see some stab Stormtroopers with spears and poison blowdarts.
Have the Force Field projector be on top of a mountain, and the bunker at the base... just to make the geography more clear.
The shuttle the heroes came in had a small force of maybe 40-50 people shoved in the back like a Normandy lander. Let them (including the Prune-faces) get some action.
Leia gets blasted in the shoulder and it WOUNDS HER badly. This is WAR dammit.
Mainly the battle should feel bigger.
SPACE BATTLE:
More ships. More types of ships. The Rebellion might have some repainted ships. Ships should crash together.
THere should be at least one Hero Shot of the Falcon flying with all guns blazing, blasting TIE fighters. Footage was shot of soldiers in the Falcon's guns firing away. That should be used.
Footage was also shot of Madine's death, as well as a female XWing pilot. These should go back in.
The guys in Napoleonic jackets can bite the dust heroically, as can some of the Alderanians. This is WAR dammit.
When Lando is escaping the Death Star, the firebursts out... and we hold our breath as a few seconds later the Falcon doesn't fly out, it tumbles out, totally scorched and barely holding together.
ENDING
Lando and Han reunite, and Han sees how totally damaged the Falcon is, black and scorched. This could be a fun moment.
Leia (arm in a sling) greets the surviving Alderanians and they kneel. A hopeful moment for the future.
Yub Yub is playing. Screw it, I love that song.
The Ewok Cheif, a translator, and a Rebel commander are talking. They're a proud people Ewoks, not all dancing teddy bears.
Luke comes back. Everyone is happy. Luke looks over and sees ObiWan, Yoda, and Sebastian Shaw.
The camera pans up above the happy people, XWings drop fireworks in the sky, camera pans up to the stars, where, as the music crescendos, the AUDIENCE POV ITSELF is pulled into hyperspace as the credits roll. People cheer.