If the BIOS can't see it, then no bootloader in the world will be able to boot off it, that I'm aware of. You could certainly write one, but it would require including enough PCI and firewire support ...
I have been struggling for quite some time now to set up multi-boot support on a new HP Pavilion dm1-4310ez sub-notebook that came preloaded with Windows 8, UEFI, and gpt disk partitioning. During ...