About the only thing I can think of is a logout hook. Login and logout hooks run as root, so it should technically be possible.
I have only one question though, do logout hooks run on shutdown?
logout hook's script steps:
1. delete home folder of the temp account (presumably you are logged in as that temp user, so your script can just reference "$1")
2. delete the user account from /Users and /Groups/admin
3. delete the logout hook entry from com.apple.loginwindow
4. delete the applesetupdone thingee
5. delete the logout hook script
Make a backup of the script somewhere off of the machine.
Create the logout hook preference in com.apple.loginwindow pointing to the logout script.
Choose Shutdown to test the process, then reboot to see if all is well.
If all is well, then you only need to create an installer package (including an install script that creates the logout hook preference) to install the hook, and logout script.
With this tested installer package on a thumb drive, you could just run it, and
shutdown.
Some good info here:
http://discussions.apple.com/thread....sageID=6891519
That is of course, if the logout hook is run on shutdowns...
That's all I gots.