Giving Domain Users Local Admin Rights
Check out the net localgroup command.
I set up something like this for a client a few months back (I know it’s not an ideal setup 🙂 but can’t remember the exact details of the single line command file I used. It was something like
net localgroup Administrators /add “domainname\Domain Users”
You can do it with domain policies but adding a line to the startup script was the simplest option at the time.