I am currently setting up an image for Sysprep. Unfortunately the PC will need to be joined to the domain to install a very important piece of software. We use a type of teller software that is web based, but pulls down modules from the server. Even though the modules are small it can take a good 45 minutes to install. The only way to install the software is by using a domain user.
Is there a safe way to join the domain, unjoin, and then sysprep?
I've done this many many times - mainly so I can use WSUS to pull down the windows updates locally instead of using MS's update servers.
Do exactly what you said. Build the machine, join the domain, do your setup, take a pre sysprep image, unjoin the domain, reboot, sysprep, take image.. deploy image, join domain.. done.