Problem is that the B&W and Gigabit don't use the Mac ROM anymore, they rely completely on OF support.
Unless you can trick the Biege into thinking it's a B&W, and hack the firmware... Hmmm. It might be possible, but it'd be mind mashingly hard.

Lets see.. maybe you can grab pieces of the Biege OF and implant it into a B&W Firmware update, and then force the update upon the Biege. That way, it'll support the interface with the ROM, AND the OF, but still have the B&W stuff included.