Windows 10 1703 (Build 15063) or later will mount all formatted partitions of a USB Removable media Flash drive.
This means we can not only boot from a flat-file installation of Windows 10 now, but because we can create a multi-partition USB flash drive, we can also encrypt the Windows volume using BitLocker.
Windows 10 will allow us to MBR-boot (not UEFI-boot) to an encrypted volume either by entering a short password (e.g. 8 characters or more) or by inserting a USB flash drive containing a .BEK key file for the encrypted volume.
This means we can not only boot from a flat-file installation of Windows 10 now, but because we can create a multi-partition USB flash drive, we can also encrypt the Windows volume using BitLocker.
Windows 10 will allow us to MBR-boot (not UEFI-boot) to an encrypted volume either by entering a short password (e.g. 8 characters or more) or by inserting a USB flash drive containing a .BEK key file for the encrypted volume.