Hello. I am interested in your project because it is a very good fit for my skills. I am a WordPress developer specialising in custom plugins. I have created dozens of custom integrations with WooCommerce so I know exactly how to make this work. The solution I would create would be a plugin which really just does what you said - override the add-to-cart function, though this needs to be done both on the frontend in JavaScript as well as on the backend, in PHP. My code conforms to the WordPress coding standards and uses best practice. If you have any questions for me, or you want to proceed with the project, please send me a message. Thanks and regards, Jarred Kennedy.