Why can't yaboot work with oldworld as first stage?

[Mike Fedyk <mfedyk@matchmail.com>]

As I understand it, oldworlds will read hfs partitions and try to boot files
from it.

The only problem I can think of would be the executable format of the boot
image, which is probably elf now, and would need to be another format for
oldworlds.  

How hard would it be to just compile yaboot in the oldworld
compatible executable format?  

Since it has been proposed to make ybin
compatible with oldworlds, why not take it to the last step?

I know there are technicalities, so let's talk about them.

Mike