This has been tried before. There were companies that would buy VHS (that's how old this was) and DVD movies, modify them to be clean, destroy the originals, replace them with a burned copy or duplicate, and sell them at markup. So families could buy "clean" versions of movies.

They were shut down because what they were doing was illegal, and rightly so.

I like your approach because it's done locally, which in and of itself, shouldn't be illegal. As I understand it, you're just muting the audio when bad words appear. You're just automating it.