I found a great post on setting up Windows To Go with PowerShell. http://social.technet.microsoft.com/wiki/contents/articles/6991.windows-to-go-step-by-step.aspx#z6 - this information works but assumes that you only have the USB device attached to delete and create attached. I wanted to take some additional steps to ensure you enumerate everything attached and then pick the appropriate drive:
# this lists the disks attached to the system
$disknumber = Read-Host 'What Disk would you like to COMPLETELY DELETE and REPARTITION for Windows To Go?'
# this assigns the disk as a variable to be used in the script
"you have picked disk $disknumber"
#an opportunity to get out
$disk = Get-Disk $disknumber
I have also been testing some other changes that I'll post later.