I've been the resident advocate of this idea for a long time, so at the risk of sounding repetitive, I'd like to propose something... I always felt that the rehashing of the Death Star was weak, so to make the ending more climactic, I'd like to propose that the assault on the Death Star II be replaced with an assault on the Imperial Capital.
Why? The Rebels have been working on the outer reaches of the galaxy up to the final movie. By forcing them to take on the center of Imperial activity, it adds tension and makes the conclusion more dramatic. Endor is yet another backwater, but by sending them to the Imperial Capital we signal that this truly is the last, decisive battle.
By ridding it of the DSII, we also make it clear that the threat is very different than the threat in the first movie. Here the risk is that the Rebellion has been drawn into the belly of the beast to be destroyed. I know there's already been talk of adding Coruscant to the finale, but I think that if that's going to happen, it might as well be used as a means to getting rid of a rehashed plot element.
How? Well, there are ways:
1. At the opening of the movie, replace the entire matte of Endor and the DSII with a matte of the Imperial Capital, looking like a degraded Coruscant.
2. New establishing shots would have to be made of the shuttle's arrival at the Imperial Palace.
3. The interior of the DSII would now be taken as the interior of the Imperial Palace.
4. The Emperor's throne room would need new mattes for all the windows, showing the dingy city environment outside.
5. New establishing shots would have to be created for the Palace.
6. From the surface of Endor (now a moon of the Capital) we should be able to see the Imperial Capital.
7. Luke's confrontation with Vader in the Endor Imperial base could now be set in a building in the Imperial Capital - perhaps a massive and foreboding detention center. New establishing shot would be needed along with new scenery outside the corridor's windows.
8. A new hologram would have to be made for the briefing scene in which Ackbar explains the nature of the attack - the whole Imperial planet is surrounded by an energy shield generated from the moon of Endor. In order to attack the Palace, they must shut down the generator, send a team to fly into a service shaft which travels underneath the Palace and have them destroy the Palace's energy reactor, which cause a chain reaction destroying the entire palace. The only reason this attack can proceed is that the Imperial fleet is "spread thin throughout the galaxy in a vain attempt to engage" the Rebels. This, of course, is all a trap to bring the Rebels onto the Empire's home turf.
9. The Falcon's attack on the DSII's surface would have to be altered so that it appears to be flying along the surface of a city before ducking into the service shaft.
10. The big dramatic conclusion! The Imperial Palace would have to explode in dazzling fashion just as the Falcon escapes the blast. This would probably require a whole new CG model, like the establishing shots mentioned above.
Well, that's my offering. Take it or leave it, I just felt I had to say it.