As much as I understand the boot process so far, boot0/chain0 are only there to load boot1h from the start of a partition.
boot1h in turn is able to read HFS+ to load a file called "boot" from there.
That's all these do.
Hence, wouldn't it be also possible to use some other PC boot loader and tell it to load "boot" from a NTFS or FAT32 volume instead? "boot", after all, has to provide all its own HFS reading code anyways, doesn't it, so it shouldn't matter how it got loaded, does it?
And then, I'd expect, that "boot" scans all available drives and partitions on its own.
Would that work? If not, where am I wrong in my assumptions?