Preparing for a merged /usr in Debian

That's why merging /usr in all popular distributions is particularly important. Only after that it will be possible to change shebangs in scripts from #!/bin/bash to #!/usr/bin/bash. After some (long) period of time it will be possible to remove /{bin,sbin,lib} top level directories, as shebangs will no longer point on them, reducing top-level clutter and achieving separation of concerns, as you proposed.