Some good ideas in here. I like the idea of allowing users to selectively unblock domains, so that eliminates the whining we've heard about how defederating is taking away their freedom of choice, even though it should be the instance's freedom of choice not to host meta's hate speech.

Also, as to the concluding paragraph, I agree. I've said before this is a good problem to have. The fediverse will get tested against the most dominant social media corporation in the world. If they adopt it and it becomes the de facto standard for many other social media platforms, then it will grow beyond their capacity to control it very quickly.