I'm not suggesting that /usr/share/.../ should be the only place to find
.egg-info directories. Simply that pkg_resources would scan
sys.path+['/usr/share/.../'] and treat the ones found in /usr/share/.../
as if they were in /usr/lib/pythonX.Y/site-packages/. Everywhere else
that a user could put Python packages (e.g.
/usr/local/lib/pythonX.Y/site-packages/) is fine to put whatever the
user wants. Eggs, .egg-info/; it doesn't matter. It doesn't need an
alternate location. Debian packages need to be more disciplined, but all
Debianized Python packages are installed to
/usr/lib/pythonX.Y/site-packages/ so we only need the one alias, not many.
It's possible that only the DD in charge of packaging setuptools will
have to concern himself with coding this.