They don’t even need to do that: just making e.g. Netflix or YouTube display a message like “Your experience is bad right now because your ISP is trying to double-charge for your traffic. Click here to call them…” would get an enormous amount of leverage.
Google actually already has something like this in place for YouTube.
Not specific to net neutrality (or lack thereof), but if they detect that your access to YouTube is slow due to network congestion on your local ISP, there's a popup that essentially names and shames your ISP by redirecting you to this:
