Late followup to this. It is non officially planned and Kristian is working on it. And if he is working on it, it should arrive by the time Wayland is slated to take over from X.org.
A libwayland application may start up a proxy compositor on the machine (server, appliance, closet PC in your example) and blit the compressed damaged regions over the network. Or an RDP (or SPICE, VNC) server could offer the proxy compositor (even through SSH).
He also has commented on examples of a rolling hash algorithm to instruct the client to reposition damaged regions vs re-blitting their contents.
Now that the 1.0 specification has been released, I hope to see others helping out in the area of remoting. Nobody's going to deny that Wayland can't do everything X11 can do today, but they're also not positioning Wayland to replace X11 _today_.