I smile at this discussion, having gone through this same thought-cycle so many times.
I claim this is motivation for the separation of a graphical client workstation, simpler and separate from the server, having ONLY a single-user identity at a time. In other words, re-implementation of the XWindows approach.
I think that identity, access and security friction as we see in this discussion will eventually push the pendulum back in that other direction. Except for those who dont mind the in/decrement in complexity and responsiveness in an installation that provides both. In the data center this separation is enforced for many years; X-Windows is not installed on servers. There's almost never a need for it there and it presents another attack surface.
In sum, we need a (Debian-based) live distribution that provides only an X server. And focuses on network and graphics responsiveness (resident in RAM where possible). Trading-off against other performance targets. Leaving little to no footprint on the local disk besides kernel image and initrd. Of course knoppix and floppyfw are the examples. Just tighter and focused to that role.
Your thoughts?
From wikipedia on X Windows:
X allows a graphical terminal user to make use of remote resources on the network as if they were all located locally to the user by running a single module of software called the X server.