I'd argue the most important of the changes Musk has suggested are transparency around the recommendation and ranking algorithms and the datasets used to train them, and increasing the character count of posts up to 512-1024 characters.

There's a lot of mystery about how these algorithms are designed, trained and used in practice - and not just at Twitter - and having all that open-sourced would in itself be a huge benefit to the whole world. A whole lot of authoritarian outfits are trying to use these algorithms as a means of social control and popular opinion manipulation - and not just in places like Russia and China - and it's reached the point where understanding how such systems are used is kind of critical to preserving the future of non-authoritarian society.

As far as long-form Twitter, at the very least doubling the character count would allow for a lot more nuance in Twitter communication, which is defintely lacking at present. And no, multiple posts in threads don't really work for that purpose because of the way those individual posts are distributed elsewhere, without context.