From all of their claims about "traditional UNIX" you can tell they haven't used many traditional UNIXes. I seem to remember on Irix that ifconfig was under /etc for some reason, that was always fun to remember.
Also anyone who has ever used Solaris should shudder at the thought of making the Linux userspace more like theirs, although I have to admit I haven't used Solaris 11 yet.
I ran a large cluster where /usr was mounted read-only by all the compute nodes,
which PXE-booted with a bare-minimal / in initrd (just enough to mount /usr). Worked well most of the time except for shutdown, when the initscripts just couldn't handle the idea that /usr would go away at unmount-all time. I suppose this proposal wouldn't necessarily make things worse, but it will make it harder to populate an initrd with a minimal / setup if no one is even pretending to try to have a version of mount that can live w/o /usr anymore. I guess you'd have to make it out of busybox or something instead of just copying over selected files from /bin, /sbin, and /lib.