Copy your boot.ini onto a boot floppy with a set of "minimal" firewire drivers, redirect your boot.ini path to whatever the RDISK volume for your now externalized firewire drive is.
Not wishing to elongate this thread any longer, but I doubt if that will work.
a hacked boot.ini on the floppy will still not 'see' the firewire drive, and adding drivers to the floppy wont help either, as theres nothing there to use them.
There ARE custom Win2k/NT boot floppys you can build, but even then I'm pretty sure they only support IDE drives that for some reason the bios won't boot off of.
In short, If the bios wont boot off the firewire drive (ie, if fdisk from a bootable DOS floopy) can't see it ( see
http://www.freedos.org/ for more info. ) then you are out of luck. You need INT13 bios support, to boot.
-Jar.