Hi,
(f) The scheme should function without UEFI. There are plenty of
non-UEFI systems out there. This means that the bootloader might need
to live in a BIOS boot partition, or in flash, or in ROM, or in other
strange places.
Now let's think this through. You're proposing that $BOOT be
the ESP.
This fails (f) entirely.
Well, no. You can have both ESP and bios boot partitions, and configure
grub-pc to read the BLS config from the ESP ...
cheers,
Gerd