Well does the above work?...
I don't know. And as you noted, I would have to get rid of my XP entry to do that, so its probably not the best option...

I might try it sometime, but right now's not the best time. Besides, I thought "ntldr" is still used by BartPE? I am aware of the "setupldr.bin" file's existence, but thought it was for loading BartPE into the ramdisk.
On my USB stick, the ntldr and ntdetect.com got copied into the root along with the rest of the files needed for BartPE, while there was no boot.ini, but a "winbom.ini" file instead. And the "setupldr.bin" is in my
minint folder on my USB stick, not the root.
Addendum:
Also, take a look at the
Supported Operating Systems page in the wiki...
I'm not sure, it may be outdated, but it clearly states in there that WinPE 1.0 is supported...