I might be able to do the "single" album ... Right now, I don't think soups ever mix tunes and playlists together, so I'm sure it will initially break things. The threshold one is kind of tricky, because once i delete the playlist that, say, only contained 3 (and your threshold was 4), then if you retag and cause a 4th to be created, the soup wouldn't know that there used to be 3 there, and that now the 4th causes it to qualify without a full rescan ...