This is a bit tough but say a standard API that npm packages can expose so that runkit can benchmark and compare different packages that implement the same thing. That's probably too hard but maybe there's an idea there.
Another idea would be to determine how many npm packages a package depends on by walking the module dependency tree. This could produce a code volume metric for browser applications. E.g. If you use this package in your browser it will require up to 100 MB to download with all its dependencies!