@ Rootman
If you follow the procedure on first post of this topic http://reboot.pro/to...boot-optional/ you will be able to also boot directly from Windows bootmanager your mentioned ISO as MBR (without need to load it in Ram first) and also as UEFI, and still keep E2B and agFM on your USB device.
I think with the mentioned approach we may loose E2B .imgPART capability (I haven't verified), but if using agFM or WinNTSetup it will not be missed. And additional Wimboot VHD capability will be added:
Allowing to diskboot Wimboot VHDs (on Bios + UEFI + UEFI with CSM mode active) or Ramboot Wimboot VHDs (on Bios + UEFI with CSM mode active).
alacran