There is an alternative for the normal Windows shutdown command. Normally we use something like this to shutdown the VM in packer.
"shutdown_command": "shutdown /s /t 10 /f /d p:4:1 /c \"Packer Shutdown\"",Replace it with
"shutdown_command": "c:/windows/system32/sysprep/sysprep.exe /generalize /oobe /quiet /shutdown /unattend:a:/unattend.xml",and on the first vagrant up the box will boot with an out-of-box-experience (OOBE)