Different config options for different X servers?

[Seb Wills <saw27 mrao cam ac uk>]

I use gdm to start several local, 'static' X servers. One is an ordinary 
X.Org server. The others are Xvnc servers. In reality these provide remote 
access (since a remote VNC client of some kind connects to them), although 
gdm thinks of them as local X servers because they are not via XDMCP.

I'd like to be able to specify different settings for some gdm options for 
these two classes of server. For example, I want Reboot and Shutdown 
buttons enabled on the local X.Org display, but not on the VNC displays.

Is there any way I can do this?

Since gdm already has sensible and/or separately configurable behaviour 
for what it thinks of as "remote" logins (i.e. XDMCP), the neatest 
solution would be to be able to specify in an X server definition that gdm 
should consider it to be a "remote" login even if it is not via XDMCP.

Another option I pondered was running two instances of gdm. I'm guessing 
that would get a bit problematic though since gdm integrates so closely 
with the system.

Any thoughts? I think the ability to define a seemingly-local server as 
remote would be a useful feature, and perfect for VNC servers.

cheers,
Seb