How difficult would it be to make the equivalent of Windows Terminal Server with Wine?

[Andrew Quigley]

What I would like to be able to deploy would be a system which runs 
multiple Win32 compatible desktops and multiple logins on a server, with 
the clients accessing the desktops via RDP or ICA protocols.  How many 
of the pieces required to accomplish that already exist, and what pieces 
have yet to be built? A quick search on freshmeat shows me a few 
different rdp clients, so it looks like the protocol spec is known. What 
would be involved in creating a RDP server that shows up as a video 
driver as far as the win32 programs are concerned?