@Rollerphant:
What have you tried so far for the query? I'm thinking so far that this may be impossible, unless you first set up child nodes for each AlbumArtist, which could easily be a laborious process. Even if you can automate that part with something like MagicNodes, I don't know if MegaDJ would be able to interact with those nodes. But, my thinking is, if you can have MegaDJ nodes for each AlbumArtist, then you can create a master node that rotates X number of tracks from each of those AlbumArtist nodes.
Perhaps twinbee may have other ideas, however. I hope you're able to figure this out! If I think of anything else too, I'll let you know.

