Problem: Insurance companies "unfairly" exclude children with pre-existing conditions from most sorts of health insurance policies.
Solution: Make them do it anyway.
If a thing can be done profitably, in a genuinely free market it will eventually be done. If it can't, it won't. Forcing someone to do it anyway out of a misguided sense of what's fair doesn't magically make it profitable, it forces the companies suddenly under the government's thumb to flee the market.