I'm all for reinventing the soundtrack, but I wouldn't want to lose EVERYTHING (I like the Trade Federation March, for example). But yes, all the Film Soundtracks, Shadows of the Empire, and other John Williams scores would be appropriate sources to draw from. The Planets and Rite of Spring are other works to draw from (as Trooperman has in SotDS). As for the topic at hand, I think sprinkling around Duel of the Fates is a great idea. The soundtrack is going to be one of the hardest, but one of the most enjoyable alteration we make.