I've just had a moment to read PEP-376..
I seriously question the need for a new .EGG_INFO directory...
Given that a typical site-packages directory doesn't have many files in it anyway.
Typically, it will contain 20+ project/package subdirectories or .EGG files/directories.
Why not keep the .EGG_INFO files in the site-packages directory?
It hardly has many files in it anyway.
It seems so much simpler to use site-packages and doesn't add any extra o/s overhead (yes - more directories does slow a system down - slowly - but surely).
From a pure python perspective.. another directory isn't needed.
I think we could do a lot more to manage what we already have... before making new wholes for mess to go in.....