Notice that there's another issue: maintainer is not written in the
Metadata if author is provided.

Plus, PyPI has its own role system: owner+maintainer, that has nothing 
to do with the package Metadata (it's just who registered the package
and who was granted some access)

So at the end, if we don't manage roles at the Metadata level, 
I don't see any good reason not to have one single 'authors' option
with a list of authors.

Having the mail like you've described is a good idea too.