When you say “force demand to spread out more”, what policies do you propose, and how confident are you that this is both easier to accomplish than the YIMBY solution and leads to better outcomes?
My default (weak) assumption is that a policy requiring more explicit force is more likely to produce unintended negative consequences as well as greater harm if unpopular. So a ban on A has a higher bar to clear for me to be on board than a subsidy of B over A. My initial reaction to the sentence “force demand to spread out more” is both worry at how heavy-handed that sounds at first blush, as well as confusion as to what the upside of this is over the YIMBY solution, besides preserving the utility of some currently-exurban houses/land that would otherwise go unused. That’s good, but I don’t see why it’s so good that it justifies not pursuing greater density instead, since as you say the money is already in the city.
This might sound either flippant or incendiary, but I mean it sincerely: Wouldn’t creating a powerful enough enforcement regime to permanently, reliably guarantee no AGI development necessitate both the society implementing that regime being far more stable over future history than any state has thus far been, and more importantly introduce incredible risk of creating societies that most liberal democracies would find sub-optimal (to put it mildly) that are then locked-in even without AGI due to the aforementioned hyper-stability?
This plan seems likely to sacrifice most future value itself, unless the decision-making humans in charge of the power of the enforcement regime act purely altruistically.