Ahh, I see...
The Playlist Is Any rule can point at a Playlist Group, and it'll pull children automatically.
That's similar to the system I use to sync my Library to iTunes with MCiS. You can make a "master sync" Smartlist, that points at any other Playlist Groups. The only thing you can't do is point directly at the Playlists group itself (which contains all of the other Playlist Groups). That's because technically, the Playlists item isn't a Playlist Group, it is a root View Item.
But, so long as you don't often add new top-level Playlist Groups, you should be able to pull it off.
Make a Smartlist at the Root of the Playlists part of the tree (or wherever, but that'd be a good place) called something like Master Sync List. Then, point your sync at it.
HOWEVER... I'm not sure this will help. Is you goal to get MC to actually sync the Playlists themselves over to the device, or the contents of the Playlist over to the device?
If the latter, this method will work fine.
If the former, then it won't.
But....
The Handheld engine doesn't automatically pick up new children when added to a Playlist Group? Are you sure?
EDIT: I didn't read properly. MrC and you already covered enough above to explain what you're looking for. Ooops.