I understand the problem but I can't think of a way.
Unfortunately (as I understand it) iTunes keeps the track metadata separate from the files rather than writing it all in tags.
There may be some form of iTunes metadata manipulation software (if you go down that path take a copy of your library before doing anything to it).
It's a lot of work, and probably not something you now want to do retrospectively but I found to create a PlayIt Live library making a folder structure matching the categories you want to have and dumping tracks as appropriate in to that works OK.
You could then import in to iTunes from those folders but it doesn't work for your existing library.
As a more general observation, PlayIt Live has different applications to iTunes so possibly keeping each application to what it is best at might be the way to go.