Ask HN: If you could work on anything, what would it be?

If you made fuck you money or found a powerful patron (e.g. working SO) and could work on anything you wanted, what would it be? You wouldn't be beholden to market pressures or the latest fad ideas. What would you work on if you could slow down, and instead of trying to iterate the idea-users loop as fast as possible, you figure out what you should be building, instead of building what you can (profitably).