Calling Google's bluff and seeing if they would willingly cut their users off from half the web seems like an option here.
Based on previous history where people actually did call google's bluff to their regret, what happens is that google trusts all current certificates and just stops trusting new certs as they are issued.
Google has dragged PKI security into the 21st century kicking and screaming. Their reforms are the reason why PKI security is not a joke anymore. They are definitely not afraid to call CA companies bluff. They will win.
It's one of those things that has just piggybacked on top of WebPKI and things just piggybacking is a bad idea. There have been multiple cases in the past where this has caused a lot of pain for making meaningful improvements (some of those have been mentioned elsewhere in this thread).
Sure, they supported the nascent HTTPS very early on, but most of the web thought that certificates were "too expensive for the likes of us", and so only really banks and the like actually adopted HTTPS. Most of the internet was still HTTP only for years after HTTPS was available.
Only when LE came along and started offering free certificates and facilitated a massive uptake in HTTPS websites were Google ever in a position to default to marking HTTP as "insecure and dangerous".
I've got no figures, but I suspect that if LE were to kick their heels in, that Google wouldn't dare risk half the internet not working using their browser. I'm sure that would be some people who didn't want to be collateral damage if there was a standoff and would switch to a CA that complied with Google's will, but I suspect most people would be happy to see Google challenged on this. And end users would hopefully discover that every other browser still worked, just Chrome had broken, and Chrome would quite rapidly fall out of favour.
Google didn't just make TLS popular, they made it secure.
It's for your own good dontchaknow!
Given that LE renews certs every few weeks that wouldn't take long
