I'm all for improving the situation with around auto configuration of
hardware, but with all due respect, I think you guys are trying to solve
the symptom, not the real problem. In my view you really want the X
server to be able to export an API for software higher up the stack
(GNOME, KDE, etc.) to configure the X server. You also want to
reconfigure it while it's running. It seems to me, that putting in an
mediator, for basically writing out configuration files, is not the best
API for doing this. I could be wrong though. Ideally the X server
wouldn't even touch hardware before someone used that API to say "Add
monitor, Add input device, blah blah".
Anyway, with the right API in the X server (which would probably be
exported through D-BUS), I should be able to write a daemon, let's call
it gnome-input-manager, that runs in the desktop session as user davidz.
This would also allow said daemon to disable the touchpad when I connect
an external mouse or, for more fun, to disable it around intervals where
I'm punching the keys. The reason you want this in the desktop session
is that you want to query the locally logged in users preferences from
e.g. gconf or whatever.
Just what I personally think.