Quoting Ansgar Burchardt <ansgar@debian.org>:
This could also be seen as a slower path to merged-/usr: programs such as `sed` would be in both /bin and /usr/bin and hard-coding either would be fine (as with merged-/usr, but not without). Less static files would be on a read-write root file system (if /usr is a separate read-only fs). In case a later Debian release would merged-/usr mandatory, the conversion process would be less problematic as no files would be left to move (just replace individual symlinks with a directory symlink).
Reminds me of the long /usr/doc -> /usr/share/doc transition in potato times. And we did not even have dh in those days. Sounds good to me!