@cadalpias
Booting WinPE4 via PXE is the process to go. You can configure a WinPE to contain more than one boot loader and the system can pick whichever is required from the client to boot off. I have not yet looked at the DS WinPE, but creating one with the Windows Kit actually allows to have multiple boot loaders and also define the order (means if loader #1 does not match, fall back to #2 and try to use that one).
@Dave
the BIOS config should look like this:
- Disable UEFI Boot Sources
- Move the NIC to position #1 of the Legacy Boot Sources
In case you receive machines delivered with Win 8.x preinstalled, you want to take into consideration the disk has to be wiped first and for us it turned out best to use Diskpart.
-BBC