Allow only some clients to pull WNOS.INI information

We currently have approximately 60 Wyse terminals with ThinOS spread around the company.   I am attempting to set up a WDM server, and when testing it, the issue I found is that now that there are DNS entries and a FTP server, existing terminals will automatically grab the WNOS.INI file on reboot, and since it's not set up for them, they fail to boot.

I created MAC specific files for the two new terminals I was deploying, the edited the WNOS.INI to just say "include=$MAC.INI", and that works for them, but an existing terminal just boots up and comes to a login screen.

If I manually program the file and WMD server settings into each new terminal, and don't have DNS entries, it will work.  But is there some way to have the INI tell the terminal to use it's current configuration if there isn't one on the WDM server?