Just don't think you will make such proxies disappear with technical means -- in particular not where they are mandated by law.
I fully agree with you when we're talking about people trying to make money by modifying 3rd party traffic.
But I leave it to the relevant legislatures (and their electorates!) to decide with respect to libraries, schools, prisons, financial traders, spies, police offices and so on.
With respect to HTTP/2 there were two choices:
1) Try to use the protocol to force a particular political agenda through.
2) Make the protocol such that people behind manipulating proxies have notice that this is so, and leave the question of which proxies whould be there to the political systems.
Implementing policy with protocols or standardisation has never worked and it won't work this time either.
At the end of the day: IETF has no army, NSA is part of one.