I want there to be a new subplot with Luke having a recurring nightmare (the result of Vader attempting to get into his head), and I want his face to be scarred to hell from his last encounter. He'll, like I said, be an outcast from the group until the very end. Also, he has, again, used this time to train with Yoda, as you mention in the story. Luke's first scene should be him carrying out a successful version of the cave scene, to show growth.
There does need to be further training and heavy consequences.
ROTJ rips the viewer away from the Luke Skywalker we know by showing him as wise and confident as Obi-Wan right from the start. The discrepancy is hardly explained by the amount of time between the two stories (it's scant); the only explanation is that Luke was essentially rewritten as a character. His development should have been gradual.
The slaves I added because I realized that there was a humanity aspect missing if it were simply to be rebels vs empire. I figured they could be a mix of various humanoid races from various worlds, and could supply information to the alliance about interiors of various settlements. Also, the film needed some sort of pulse-pounder before the 3rd act.
It's not the plotline that would've come to my mind immediately, but I'd be interested in seeing it play out in some form.
I figured Lando would be feeling really bad about the events of the last movie, and constantly trying to regain trust from Han, who would be unreceptive to his attempts. Maybe just as simple as a role-reversal for the sail-barge battle, making it so that Lando saves Han. In any event, trust would be restored by the time the battle was underway, and Lando would get control of the Falcon for the air-strike. On 2 conditions. 1. Not even the tiniest of scratches. 2. Chewie must come with. Of course, he ends up breaking the first one.
Wish there had been a conversation between the two about the betrayal. I guess Han saw Lando's assistance in his rescue as being enough confirmation of good will, but realistically (character personalities need to remain consistent and realistic, even in outlandish settings), there probably would be hard feelings there.
Who the heck was the Millenium Falcon's new co-pilot in the DSII mission? The fish alien. He had zero personality to speak of, really.
I want the Death Star II not to be destroyed. 1. it's a change of pace. We've had the bunker scene before and it's too run of the mill for Star Wars. 2. It's a more effective and Jedi-like solution to end the fighting. Maybe it could be destroyed as soon as its passengers have been taken off, as more of a symbol of the Empire's dissolution than anything else.
This is where we contrast, I think. I would've left the Death Star II out of the equation altogether, for the same reason of it being run of the mill. Recycled plots in the EU, or way down the line in the films, can be forgivable. But this is in the same trilogy as the first Death Star. Even as a kid, without analytic abilities I have now, I found that to be an odd choice, if not a bit lazy.