1. Post-install steps included in setup.py. That should be covered by the support in Metadata 2.0. I'd also be interested in how much of an issue omitting the postinstall would be in practice (for instance many such steps just set up "Start Menu" type shortcuts, which are not essential for the package to be usable).
On windows, we use wheel convert to convert binary installers like pywin32 to wheels. But the post-install step in the setup is mandatory for pywin32 to work (it is not a mere Start Menu customization). So this is what we do: wheel convert pywin32-217.win32-py2.7.exe pip install pywin32-217-cp27-none-win32.whl In this case pywin32_postinstall.py is not run and we need to run it manually. I do not know the specifics, but pywin32 predates wheels, I don't know if it can be made to be installed so simply. D.