Just to spitball some more ideas, I've been thinking of a different way to open the film that can incorporate the "Bothan spies" idea to some degree.
I've made a mock up of that opening here: http://vimeo.com/35740289
The idea for this being that we don't see the Bothans stealing the Death Star plans, but we do get an impression of the aftermath of that. Perhaps something like this video combined with an opening crawl like the one below could work for that:
"The Rebel Alliance has learnt that the GALACTIC EMPIRE is secretly constructing a second DEATH STAR, one even more powerful than the first. When completed this battle station will spell certain doom for the Alliance.
In a desperate bid to avert destruction Princess Leia, leading a band of Bothan commandoes, fought her way onto the Imperial facility on Had Abbadon to steal the Death Star plans. At a great cost of life, Leia and her team were able to escape and deliver the plans to the Alliance.
THE EMPEROR has dispatched his apprentice, DARTH VADER, to Had Abbadon to ensure Death Star is safely completed. However Vader is distracted by his quest to locate his son, Luke Skywalker..."
Using additional footage, I've started work on a scene between Vader and Boba Fett, the idea here being that we see Vader send out Fett to find Luke. This could add some tension to seeing Fett in Jabba's palace, his presence there now being part of Vader's plans to capture Luke.
Finally, this is just the way I think see these opening scenes could play out:
Opening Crawl.
Vader's Tie Fighter arrives on Had Abbadon.
Vader contacts Luke (on Dagobah) through the Force.
Luke senses Vader whilst building his Lightsaber, is called by R2 to Yoda's hut.
Luke goes to Yoda's deathbed, meets with Obi Wan.
Bobba Fett meets Vader on Had Abbadon, is sent after Luke.
Vader leaves for his Star Destroyer, Fett heads to Tattooine.
Vader's Star Destroyer arrives at the Death Star.
Luke arrives at Tattooine; "I've a promise to keep to an old friend".
R2 and C3PO arrive at Jabba's Palace.
PS.
I've had a quick flick through the Dark Empire audio, only a few Billy Dee lines and probably not of much use. To quickly paraphrase the lines, so far I've found:
"I don't think our field weapons are doing much against those huge Imperial Walkers", "Get Down!", "If we tell the Imperials that, maybe they'll break for lunch", "Luke's growing strong. Very strong. I've not seen anyone like that since... Vader", "You okay Wedge?", "Han Solo; you old space pirate.. what are you doing here?".