Yeah I would have tried your technique myself except that my MBR-fiddling skills are a bit rusty, so its easier to screw up.
Well, you will never know if something works until you try it.
Isn't it funny that I have been accused of attempting to prevent you from discovering new ways?
The issue Sha0 was referring to was about the possibility that due to a non-standard BIOS a perfectly compliant GPT disk may not boot on a given machine and that if made bootable on that particular BIOS (with some hybridizing or other trick) that same disk unmodified might not boot on another given machine with a particularly "strict" (or "wrong") EFI implementation.
But this is not your case, you only have to make a "good enough" GPT disk for Windows that is also "good enough" for the stupid BIOS you have, there is no real need that the disk is integrally compliant with *any* EFI firmware.
So you can well use a hybridized MBR and each and every trick (+ 1) fair and unfair as long as you obtain the expected result.
Which checks does the BIOS make?
- that at least one entry in partition table starts with 0x80
- that the partition table entry that starts with 0x80 has a "known" partition ID
- that the partition table entry has valid CHS addresses
- that the partition table entry has valid LBA data
- that there are no overlaps in the 4 partition entries
What checks does the Windows loader make?
- that only one 0xEE partition exists
- that that partition entry does not have the 0x80 flag
- that no partition entries have the 0x80 flag
- that no other partition with "known" partition ID exist
- that no other partition with a "known" partition ID has the 0x80 active flag
Once you will have (through experimenting) a more clear idea of the behaviour of both the BIOS and of the Windows loader, then likely one or more valid solutions to your specific issue can be found (and VERY likely they will be a hack of some kind).