Cynically, does a bank care why zipcode is correlated with failure to repay loans? Forcing the bank to act as if the probability distributions are different from how they really are sounds like a very awkward way to redistribute wealth. Maybe the right answer would be reparations for whatever society did to everyone in those communities and then total freedom of association for banks and others to give loans as they see fit. Another option would be to give a bad credit subsidy to people in the cases where their low estimated trustworthiness is judged to be due to someone else's error. For example if a factory gives me lead poisoning, my interest rates go up because people with high blood lead content are less likely to keep good credit, but the factory has to pay the difference because they were liable.

This reminds me of the argument for the UBI. Instead of having thousands of tiny chairty programs sprinkled all over society, why not let the economy make itself as efficient as possible and then hand out the charity in units of dollars?