allow more efficient customization from autounattend answer file
currently the autounattend.xml is both limited and slow. Things like network setting updates cause reboots, and other things like the Administrator name can't be changed at all.
Windows needs to be more inline with tools like cloud-init in Linux: it should be extremely fast to make boot-strap changes to the OS. In the world of auto-scale, seconds count and autounattend.xml sometimes takes minutes.