[Sun 14/09/28 10:52 BST][p0][x86_64/openbsd5.2/5.2][4.3.17]
zsh 1044 % sudo pkg_delete bash bash-4.2.36: ok Read shared items: ok
In reality, this is only possible, because, as a sane operating system, there's no dependencies on anything other than a POSIX-compliant sh, of which there are several available.
To me, just another reason to avoid specific shells and just target POSIX. When the shit hits the fan, you'll have somewhere to hide.
When I tried to do the same on my work (FreeBSD) box, I came up against several issues. The main one being that lots of packages specify bash as a dependency.
At some point, I'll write a blog post about the functions of that server, and how I've hardened it.