SUMMARY Maybe is a dumb idea, but how about adding the option to enlight to the user if a file in his system is part of this or that package? So I understand somehow which ones are heaviest and I can clean up from the PM instead of deleting unsafely system files. I'm on Arch Linux and I think that should not be a problem with lots of distributions (apt, pacman, dnf, ecc)
It's not a bad idea but I think this is a job for a package manager. They know how large a given package is and how to remove it (or if it can be removed at all -- dependencies etc.).