I'm unfamiliar with the Windows commands (or for that matter any command line partitioning) but it didn't look that impossible to me, bonzo.

One thing I might question is what you do if you disk already had partitions but I'd probably use gparted live to set the partition table type and delete any existing partitions. I could even try to prepare the disk with new partitions that way. Going by his example, I think the first partition would need to be fat32 sized at 512Mb and the rest of the disk would be a ntfs partion. With a larger disk, you could opt to create more than one suitably sized partitions rather than one big one. Once created, the fat32 partition would need boot and esp flags set. I think Windows would assign drive letters which you would need to work out on booting to the ISO.