can’t help thinking it’s kinda rhetorical.
Danny, the closest I saw to an idea about how this would be implemented is that somebody (prominent) asked me why the ability to recognize file types wouldn’t suffice. The implication was blocking all BitTorrent or maybe all MP3.
In your ultra quick guesses on how it would be implemented you hit the nail on the head. You have to mix layers and pull the application deep inside the network to ensure legality, and that sacrifices neutrality.
My guess is that a skilled practioner couldn’t come to any other conclusion, but that’s only a guess, given that I haven’t studied this for real.
The internet engineers have to do this for real in order to get the point across. It can’t be a 50 word comment in this thread, it has to be a white paper or many white papers.