I do like this idea, more difficult to do without access to the original source code, and I think that this would be more "reverse engineering" rather than cleanrooming, as you don't have the same concerns about copyright violation if you're working from a binary.
It works. It is hooked up to Stripe. You can upload your package.json and receive a fully cleanroomed set of dependencies to use yourself. It is up to you to determine whether this is a compelling product or a warning to those who care about FOSS.