The CPU intensive part is the only thing I'm concerned about ... With soups you end up with a lot of playlists, and to colorize back up the tree you have to check every child for dirtiness (and "coloredness").

What about making soups "immune" to the "you need to sync" warning? That way you wouldn't even be bothered? The only time this would be _wrong_ would be if you modified tunes through Emplode then came back into jEmplode. Any other time, the actual changes that you made that caused the soup to be modified would show up as dirty (i.e. in the "normal" playlists).