I could have used it a decade ago!

Now could someone please fix the BCD store mess?

Unattend has been part of windows setup for way longer than a decade.

The current form of it was introduced in Vista.

The same concept existed before, but I know less about how it worked back then.

Even without unattend, something I think people don't realize is that you can install windows on the command line. Diskpart to partition, dism /apply-image to extract files, then bcdboot to install the bootloader.