You're in this thread a lot, and you keep referencing "Mozilla has marked Signed HTTP exchanges as harmful". Is this all that important? Should Mozilla support it in 6 months as they always do with their follow-chrome-dont-lose-marketshare approach, will you also support it? In every comment, you are focusing on the "Google is evil" part of it, instead of focusing on "Are HTTP Exchanges themselves bad?", "is this an insecure protocol?", "Could it be used to impersonate a domain?".
The only reason signed HTTP Exchanges are a thing is because Google is trying to solve a problem with user experience (the URL bar). AMP and exchanges are just a different protocol and method of hosting content on a CDN. In this case, you are forced to reduce your page size and you delegate your HTML to be loaded by a third-party, contrary to that of a traditional CDN where you would (for example) create a CNAME in your DNS.
The only reason signed HTTP Exchanges are a thing is because Google is trying to solve a problem with user experience (the URL bar). AMP and exchanges are just a different protocol and method of hosting content on a CDN. In this case, you are forced to reduce your page size and you delegate your HTML to be loaded by a third-party, contrary to that of a traditional CDN where you would (for example) create a CNAME in your DNS.