The word "only" is doing a lot of heavy lifting in your sentence, but yes I think that's what this thread is requesting. Maybe subsumed in your "extend ACME and CA/B" is that it'd take a lot of effort to get CAs on board. And I don't see commercial CAs getting excited about something unless they could charge a lot for it. And non-profit CAs like Let's Encrypt have enough on their plates just trying to keep HTTPS going. All of which is why I was suggesting someone would need to put together so...
