Hi!
The core-bios would boot up like most BIOSes do now, by requiring lilo or something like that. But with the user-extention to support ext2fs and FAT, you could then do something closer to the Sun bootloader.
Sun bootloader does *NOT* have any filesystem hardcoded. It just knows how to boot initial 8K block from SCSI (something like MBR) and pass command line to it. It is this 8K block which knows filesystems.
I don't think bios should understand fs: you don't want to have partition just because of booting. I do not think that we should change current system anytime soon.
Pavel
PS: Did anyone try to flash that bochs bios into flash and see if it boots?