Allow configuration of domain OU from GUEST OS PROFILES GUI
Currently, the only way you can have a machine join a domain and have its computer object move to a specified OU is either thru unattend.xml or by using PowerShell to edit the Guest OS Profile.
The PowerShell to do this is simple:
Set-SCGuestOSProfile -DomainJoinOrganizationalUnit "OU-GOES-HERE"
There is no reason why this cannot be a text box in the console GUI. Under the domain textbox, put a checkbox there that says "move from default OU" and textbox for the OU string underneath it.