Pretty good idea and nice idea presentation.
Many RealDrums files have "one shot" samples at the end of the file. This nice thing about these samples are they are from the same recording as the rest of the file so they match the sound of the drums in the recording.
Some users create custom fills by programming a few bars of midi, insert a sample player such as the free
++ tx16wx ++ sampler, load up the one shots and have a custom drum fill.
While I like your idea I'm not sure it is practical. Each guitar and bass library from a software company like
++ Amplesound ++ typically is more than 5 GB in size.