I would like to have a way to pass a string composed of the same flags
(we can continue to use our existing "-a", "-s" and other flags) in a
consistent manner from one platform to another, to be able to adjust
driver options, kernel options, whatever, and to be able to expect it
to be similar whether I'm on amd64, macppc, evbppc, evbarm, or
whatever.
Are you talking about the UI of how the strings are written and what
they mean or how the bootloader stage that interacts with the user/prom
communicates this to the kernel? For platforms with existing
conventions, I don't see how we can interact with native bootloaders
without meeting their interface.