> I'm pretty sure back then you had no need for anything is /sbin to boot your system: you only needed files in /boot (well, initially they were placed in the root of the filesystem) and one program (initially sash, later busybox) on a floppy drive. I'm pretty sure you can do the same today and even with Fedora's "grand unification" it should still be possible. Except for a floppy drive: often contemporary systems just don't include the necessary hardware...
That seems to agree with the reasoning to get rid of /sbin /bin, etc in modern times.
The initrd will have everything you need to mount a remote /usr/ directory. You can use busybox with initrds, for example.