This just now occurred to me: using Dune footage (and the like) is basically what Lucas did with WWII footage in ANH. Sure, we'd all like to see it (yes, a portion of it is on the DVD), but we wouldn't want it in our "definitive" version. Same with Dune footage in SOTDS (in my opinion).

As far as new music, such as "Mars", that seemed to work well. For some reason, in my mind, it's ok adding new music...rather than new footage.
I guess I don't have a good reason, other than person taste.
I'm gonna get back to you on this, though. My sister has a CD of a guy who seemed to inspire Williams, because his music sounds like something strait out of ANH! I kid you not!
I can't remember his name though (maybe it IS Holst), so I'll be back with a name.

MTHaslett: BEST. IDEA. EVER.
Not to downplay what Trooperman has done! That goes without saying!