The point wasn't (only) that they were statically linked, but also that /bin and /lib were separate partitions (or even separate disks) and could be mounted read-only, could be used from tiny ramdisks etc.. In any case, though, I agree that even without the merge, it wouldn't be doable on any modern Linux system.

There are examples for both approaches. OpenBSD keeps /bin minimal and statically-linked, and it works. Solaris merged /bin and /usr/bin a long time ago, and -- unsurprisingly -- that works as well.

Frankly, as long as it doesn't bork my Debian machine when I move from Jessie to whatever Debian 9 is going to be called, they can merge all they want. At this point, seeing how many Linux systems are doing the merger, it's probably a good idea to do it, too. Packages whose developers give a flying fsck about portability (fewer and fewer nowadays because lockdown and unportability were bad only when Microsoft were doing it) already deal with both usr-merged and usr-unmerged systems (hardly rocket science in most cases), and the maintainers of packages whose developers don't give a flying fsck about portability and only develop for Linux can hope that four years from now, everyone will have merged, especially now that Debian is doing it too.