My megaproject ideas are mostly pretty standard. I'd build a high speed rail network across North America, and build and expand metro and regional rail systems in and around every city. I'd turn all cities and suburbs into fifteen-minute cities. I'd decommodify housing, and build ten million units of public/social/non-market housing, mostly three bedroom units. I'd link those last three policies together by building TODs around the new Metro and rail stops. And I'd build bicycle networks in every town and city and connect them to the TODs. I'd build bridges and walkways across skyscrapers. I'd put a bidet in every American toilet (uses less water than toilet paper apart from being more comfortable). Fiber internet in every home. A heat pump in every home. An induction stove in every kitchen. Phase out fossil fuels and power everything with Pumped Storage Hydropower and Geothermal. I'd make the US go Metric.
But my truly crazy, obsessive idea would be to bring back the French Revolutionary calendar. Or I'd purge all French influences from English.
Virtual drug test dummies. I would commission huge banks of supercomputers to simulate the human body for rapid drug tests and general research, and dump money on quantum computing. Idk if this counts as a crank project but it would definitely be immense.
The former already exists, but our knowledge of biology and medicine is still very, very poor.
You'd need to massively increase the investment in and workforce for basic science first
Yeah it's gotta be a package deal. But I also think sufficiently powerful simulations can help fill gaps in our knowledge.
Current efforts are pretty rudimentary, afaik.