So far I really like this. I have two thoughts for consideration at the present:
1) What will Boushh/Leia's involvement really be? I like the idea of including her, but what will she do? I'd suggest that she not be too knowledgeable, otherwise there'd be no need for the spies because she, a high leader in the Alliance, already has a great deal of info. She should be equally involved in the espionage itself, sneaking into whatever building or vault you have in mind. Perhaps in fact she should be the only one to survive and escape with the information, with the four agents and whatever vessel they came from could be destroyed, thus justifying "Many Bothans died..." Also, considering her desire to rescue Han, there should be some sort of ulterior motive. She's already temporarily abandoning the Alliance for a short time to rescue the man she loves, putting personal loyalty above loyalty to her people (a very human trait). If possible, I'd recommend that she get something out of it, such as some information about Jabba's court or something.
2) There is lots of enthusiasm for an opening with the Death Star. I'm starting to really like the idea of the Bothan espionage, but we will need to consider scene placement in addition with the iconic DSII and star destroyer openings, assuming something of that nature wins the vote as well.
That said, you've written out an intelligent opening so far. I am starting to really like the idea of a return to Coruscant (although I'm wondering if we should have it renamed Had Abbadon, as in the original ROTJ script, not renamed as if it were never Coruscant, but renamed like St. Petersburg became Stalingrad in the USSR--just a thought). I like their cool tactics thus far. I just plain like the idea of actually explaining what Bothans are to the many SW fans who don't know anything about EU (heck, there was no definition prior to the Thrawn trilogy). I like the idea of having them wear helmets, reducing the need for masks, as I imagine with the sort of budget we will have, it'd be easier to make funny helmets the majority of the time while keeping it realistic enough as a movie. I like seeing Boushh earlier, adding to the mystery.
If this idea passes, it will be a technical miracle for our little crew to achieve, beyond what I was truly expecting. That said, I believe we can do it if we have enough participation and determination.