Shouldn't a shortcut to a different folder work? I doesn't, but wouldn't that seem like something you would want to do. Create 1 mesh folder (for example) then have various soft or hard folder links in that folder. Links would be exposed as normal dirs to other mesh devices. I can forsee Mesh folders on the desktop getting out of hand after 2 or so.
Symbolic links (ie. shortcuts) are ignored by sync today. Soft links like junction points are followed today, but as you point out, this can be dangerous (recursive junctions, network shares, etc). I'd recommend against doing it.. :)