The reason they added the heirarchical playlists and the "play n tracks" and "always randomize" flags to the playlists is precisely so users could create custom shuffles like this without having to create special-coding cases for every user's whim.

If I understand your request correctly, I think it would actually be pretty easy to set this stuff up with playlists. I don't think it would be very much work, especially in Jemplode where Mike added some features that will let you create heirarchical playlist groups from the soup views.

Give me some more details as to what sort of interesting groupings you would like to see. I'll see if I can give you step-by-step instructions on how to do it.