There's presumably no way to allow that without also thereby allowing you to change the apparent content of the Netflix service—or of other sites! (Suppose that you could hijack the user's DNS to redirect ubuntu.com to a page that said "Thanks for your interest in Ubuntu! To download the latest version, click <a href='https://evil.com/ubuntu/ubuntu.iso'>here</a>." How can you allow one kind of hijacking without also allowing the other?)
There has been work on allowing networks to communicate out-of-band to browsers for administrative purposes. Even this is risky in general because of the phishing possibilities, among other things. Showing users arbitrary messages from network operators in the middle of the users' other browsing activities is likely to make it even easier to confuse the users into taking actions that they really didn't intend to do.
There has been work on allowing networks to communicate out-of-band to browsers for administrative purposes. Even this is risky in general because of the phishing possibilities, among other things. Showing users arbitrary messages from network operators in the middle of the users' other browsing activities is likely to make it even easier to confuse the users into taking actions that they really didn't intend to do.