I think it's still useful to have pip vendor just pkg_resources (as
pip.pkg_resources). It's easy, it gives you enough to install wheels,
and it's not the only thing you would do.

I agree.  there's 2 problems to be solved here

1) making pip a self-sufficient wheel installer  (which requires some internal pkg_resources equivalent)
2) removing the user headache of a setuptools build *dependency* for practically all current pypi distributions

for #2, we have a few paths I think

1) bundle setuptools  (and have pip install "pkg_resources" for console scripts, if it existed as a separate project)
2) bundle setuptools (and rewrite the console script wrapper logic to not need pkg_resources?)
3) dynamic install of setuptools from wheel when pip needs to instal sdists (which is 99.9% of the time, so this feels a bit silly)
4) just be happy that the pip bootstrap/bundle efforts will alleviate the pain in new versions of python (by pre-installing setuptools?)