You could probably do most of what you want generating playlists offline with jEmplode and a custom-written plugin. Basically you want additional attributes stored with the MP3 in jEmplode, so you could create a custom format for the ID3 description field (which is stored in the DB), maybe something like:

g=23,45,34;m=12,98,45;t=45,67,86;b=120

g=Genre, m=Mood, t=Tone, s=bpm

Your plugin would have to map the id's (23,45,34) with Genre titles, like Punk Rock, Hard Rock, etc. It could then create custom playlists offline within jEmplode: enumerate through the song listings, genres (or other attributes) that match go into a new playlist. It would be nice to extend the data for the MP3 file, but this is the only way I can think of (right now) to store it both in the Empeg and jEmplode. You would probably have to also come up with a good way to write this data back out to the ID3 en masse, because you wouldn't want to type all that into every MP3 you own by hand.