You can boot from HTTP (my preference for booting WinPE over LAN) using
iPXE.
The lead developer has been making some strides with the SAN boot code, such that you can hook directly into an ISO image and boot it from SAN. You can boot WinPE from an iSCSI hard disk, but if you're gonna do that, make sure that you disable or remove the iSCSI initiator from the PE, sort of a one and done that way once everything's in RAM.
A Winbuilder script would be ideal though, as MS frowns on redistributing their binaries
