If you had a basic wage (as a single person) and your employer (or the government) paid you a set amount more for each child you had, more if the child (or you) had a disability.
If housing worked so that without those top-ups could afford 1 bedroom, then with each top-up for a child you could afford one more (depending on the sex/ages of the children).
If childcare was free for all, so everyone could afford to go to work (perhaps employer-based creches, or government run nurseries?).
If the advantage for working was performance-related bonuses on top of the basic that everyone got? Perhaps linked to how well the company was doing, with extra for outstanding contributions or something?
Just a random thought really. Perhaps then, professionals would have children at a younger age, and would have more of them. Perhaps no one would resent those on benefits. Perhaps working actually would get you a better quality of life. Mums could stay at home if they wanted, until their children were at school, then work. Or work from the beginning and put their child into nursery.
Just a random thought.