This whole idea was something I toyed around with in the Starkiller Ranch thread.
If you really want to have ONLY ONE death star battle (and compress the movies down), here's a VERY ROUGH outline of what you could do with the OT:
1) Start out with regular ol' ANH.
2) Replace the DSI with DSII. The DS is not finished - it only has superlaser capabilities for now. It is shielded and in orbit over Endor (similar in a small way to Adywan's edit).
3) The DS conference will probably need to avoid any references to the DS being completed.
4) The DS leaves the protection of its shield to make an example of Alderaan.
5) In addition to deactivating the tractor beam, Ben sabotages the superlaser. (Maybe use some of the alternate/cut footage of Ben wondering around the DS, combined with one of the two switches Ben turns while deactivating the tractor beam. Notice how the tractor beam controls make the same sound as the superlaser controls that the DS gunners use.)
6) End ANH after the Falcon escapes into hyperspace and Tarkin and Vader discuss the tracking device.
7) Start ESB with the Imperial attack on Hoth. Hoth is the one and only hidden rebel base. The Imperials have tracked the rebels thanks to the tracking device on the Falcon. (The DS is not used since its superlaser is out of comission. Plus, since the Rebels have the DS plans, the imperials have become paranoid and overprotective.)
8) Show Luke training on Dagobah. The elevating X-Wing should come first. Next up, in the cave, the phantom Vader communicates that he is Luke's father. Then Luke parries and decapitates, seeing his own face. This is the last time we see Luke in ESB. He never leaves to rescue anybody because we...
9) End ESB after the Falcon floats away with the garbage. (In some way, the tracking device needs to be deactivated so that the falcon can get away.)
10) Start ROTJ with the emperor's arrival on the DS. The DS has returned to its shield over Endor for completion.
11) Cut to Luke's conversations with the dying Yoda. Han is never frozen, so we never get into the whole Jabba mess.
12) Next is the Rebel briefing. Luke arrives from Dagobah. (The others haven't seen him since Hoth). Lando is obviously an old friend of Han's.
13) Movie ends as usual.
EDIT: I forgot to add, between 7 and 8, Ben needs to communicate to Luke that he should head to Dagobah. Maybe via voice only, while Luke is in his X-Wing leaving Hoth.