Where to get a copy of Boot Camp's Unattend.xml file? I have a 27" iMac that originally had a Fusion Drive and I had previously installed Windows 10 on it using the Boot Camp Assistant.  I recently upgraded the storage in it and in the process of reinstalling everything, I opted to go with two large independent drives rather than the Fusion Drive setup.  Now I'm trying to reinstall Windows on it and it looks like I've painted myself into a corner.

When I run the Boot Camp Assistant, it complains that Boot Camp cannot be installed to a split Fusion Drive.  OK fine, I'm comfortable doing it manually, so I partitioned the drive and made myself a bootable Windows USB stick with the Boot Camp Support files on it.  It works splendidly, except for one tiny problem:

My Apple Bluetooth keyboard and mouse don't work.  All I can do is stare at the Windows Setup screen with no ability to click or tab over to the install button.  And unfortunately, I don't have a wired keyboard or mouse to plug into it either.

When the Boot Camp Assistant creates the Windows partition, it copies the Boot Camp Support files over for you and does something to make sure Bluetooth drivers load during the WinPE portion of Windows Setup so that wireless keyboards and mice work properly.  I assume it's doing this with an Unattend.xml or Autounattend.xml file.  But since I can't run the Boot Camp Assistant anymore, I can't examine the temporary environment it creates to see exactly how it's doing that.

Does anyone know how the Boot Camp Assistant loads drivers into the Windows preboot environment?  If it's just an Unattend.xml file like I suspect, you can just copy/paste the contents into your answer.
This is not an answer to the question, but I resolved the issue by borrowing a wired keyboard and mouse.