I am no in favor of MANIFEST.in removal because I find it very
convenient to define what is included in a package  and I rarely use
package_data or data_files. So I am -1 on its deprecation.

That said, having a mechanism to include directory recursively sounds
good. And people using this wouldn't have to maintain a MANIFEST.in.

Overall, I don't see a problem of having both ways.

Maybe some kind of plugin system could be created so people can
implement their own way to get a file list. I am thinking here about
the feature in setuptools that builds the file list using .svn,
so you don't have to define anything at all.

In any case, for the glob in data_files, how do you express this
MANIFEST.in line ?

recursive-include directory/subdir *.py *.txt