Some of those questions already seem to contain assumptions about the answers.
> Why are certain things getting so much more expensive? [...] How much of the cost growth is unmeasured improvement in quality and how much is growing inefficiency?
Are there other possible causes as well? If the cost growth were 100% due to improvements in quality, would it stop being a problem worth thinking about?
> How do we help more experimental cities get started? [...] Hong Kong, Singapore, Dubai, and others, have improved the lives of millions of people and appear much more contingent than inevitable.
To my knowledge (I have no citations though), the improvement meant that millions of people were lifted from far-below-western to only-sligtly-below-western living standards. Impressive yes, but how well is that even applicable to societies at our living standard. Also, are things like workplace security or environmental effects factored into the "living standard" here?
> What's the successor to the book? And how could books be improved? [...] How can we help authors understand how well their work is doing in practice? (Which parts are readers confused by or stumbling over or skipping?)
Is this a thing we want? Would the benefits of this outweigh the costs of setting up the necessary tracking infrastructure?
> Being limited in our years on the earth, how can we incentivize brevity?
Is brevity a thing we should universally incentivize?
As a side note, what's with the humblebragging? If I get Wikipedia correctly, this guy is co-founder and current CEO of Stripe and has a billion in personal net-worth. His personal opinions and descisions influence the rules for a significant part of money transfers around the world.
Yet the website and bio read as if he were just a particularly engaged intern at Stripe.
If this is the meritocracy in action, I can see why so many people have problems with it.