I would really like them to do this - just have a small team that constantly works on new scenes, either from new films/same films and have them randomise each time.
At the moment, there are 52 WDAS films out, plus 13 Pixar films.
Philharmagic currently uses 6 songs in the show.
So, if they could use even just use one song per film (although they would have even more choice if they used more than one song per film), it would probably be completely different every time you go on (although the show is set up to flow through, eg./ water from Sorcerer's Apprentice leads to Little Mermaid, pixie dust in Peter Pan leads to flying in Aladdin, so it may not be possible to completely randomise it (although Beauty and the Beast and the Lion King don't really connect into anything).
Not all films may be suitable (I've not seen everything they've done, so some may not even have musical numbers in), but it could be a way to introduce a new generation to lesser known older titles such as "Saludos Amigos", "Make Mine Music", "Fun and Fancy Free" and "Melody Time", as well as more recent forgotten titles such as "The Rescuers", "The Fox and the Hound", "The Black Cauldron", "The Great Mouse Detective", "Oliver and Company", "The Emperor's New Groove", "Atlantis: The Lost Empire", "Treasure Island", "Brother Bear", "Home on the Range", "Chicken Little" and "Meet the Robinsons".
They could have even more choice if they were to add "DisneyToon Studios", "Disney Shorts", "Pixar Shorts", "Stop-Motion Film", "ImageMovers Digital" and "Studio Ghibli" as well as the "Animated features produced by outside/third-party studios" such as The Brave Little Toaster, Thief and the Cobbler, Pokemon, Valient, The Wild and Gnomeo & Juliet.
Not saying that they would all be suitable (it would be weird seeing Pokemon in there, for example), but just looking at the possibilities,
They could also have it themed to the seasons (eg./ A Christmas Carol/Mickey's Christmas Carol scenes used near Christmas)