As others have said...
"A Musical History Of Walt Disney World" - multiple CD boxed set featuring the complete attraction soundtracks of present AND past attractions, plus area backround music tracks, live entertainment tracks, and parade/firework soundtracks. Like the AWESOME 2005 Disneyland set, all material would be sequenced by park and land, to represent a complete audio day at all 4 parks. This would have to be even more ambitious than the DL set, as that has 6 CDs devoted to Disneyland, but nothing on DCA. I am visualizing a set that includes this thorough treatment for ALL FOUR WDW parks, so we are looking at, at MINIMUM, 12-15 discs (as Studios and Animal Kingdom don't have as much history as MK and Epcot).
An excellent review of the Disneyland set can be found here:
http://www.dvdizzy.com/amusicalhistoryofdisneyland.html
I'd also like them to continue the "Imagineering the Magic" DVD series to include one for Epcot, Studios, and Animal Kingdom, and to get into the business of issuing COMPLETE DVDs of park shows and attractions (such as the Finding Nemo show already mentioned). They could do this for fireworks, parades*, Fantasmic!, show-based attractions, and even do some high quality "ride throughs" featuring all the show scenes of rides like Splash Mountain and Small World, to name but a few.
* I have an official video of the complete MSEP issued by Disneyland in the 90's, but unfortunately this was before the age of DVD, so it's VHS. Great footage, though!
This seems to have worked well for Busch Gardens/Sea World, as I own the souvenir DVDs of Believe and Blue Horizons from Sea World and KaTonga from Busch Gardens, which feature the entire shows, professionally filmed, with GREAT audio; and I also have the souvenir Shiekra DVD from Busch Gardens, which features the complete front seat "Point of View" of the ride as filmed by a mounted camera.