Why not just optimize human output like China did and incentivize education in fields that provide large scale value to society (STEM primarily) so that children are likely to deliver commensurate value to society to their costs?
That's kind of missing the point, if theres 90% unemployment, unless you arrange is so people are in education or retirement for all but circa 5 years of their life, most won't get a chance to use their skills, and no one will have money to buy the things they make anyway.