1. US Regulators can make it illegal for their banks, housing agencies, and other publicly supported entities to refuse to refi on the basis of appraisals and income. Those loans were made, and priced, with the understanding that when long rates fall they get refinanced at the lower rates.
2. A rent to own option where a homeowner has the option to sell his home to the govt. at the lower of his mtg balance or current appraisal before a foreclosure sale, and then rent the home at fair market rent for two years. At the end of two years the home gets offered for sale at fair market prices, and the homeowner has right of first refusal to buy it and finance it at current market interest rates if he has paid his rent as agreed.
The housing crisis is still with us only because these proposals were not implemented when first proposed in 2008.