While I haven’t tried it yet, I may be able to get similar functionality by setting the primary folder (the recipients inbox) to “receive only” and the secondary nodes to “send only”.
There would be multple secondary nodes, but they shoudn’t be able to see the files sent by other secondary nodes. The primary node would see all the files sent by all seconday nodes.
Ideally, the recipient would be able to set their folder as “inbox” which would 1) force “send only” on the secondary nodes 2) perhaps “publish” the existence of this inbox to devices that have paired up. Also, when the primary node deletes the file it deletes on the file on the secondary node.