Allow anyone who has enough income to pay 75% of their mortgage payment to modify their loan and become current. Make the adjustments through a combination of principal reduction, lower interest rate, and forbearance of past due amounts. Calculate the monetary value of the loan modification and place a lien on the home for that amount if/when the home is sold at a profit.
If home is sold at a loss to the homeowner then the taxpayers would absorb this cost.
This plan helps every homeowner who is "underwater", behind on payments, or otherwise struggling in this market. Yet, there is a disincentive for people to utilize the plan unless they need to.
This plan helps the people who worked hard and "played by the rules" by establishing a floor under home prices, and putting upward pressure on the market. Also, if there situation has deteriorated due to the drastic economic conditions, they would be able to refinance and take advantage of this plan even though they are not currently behind on their payments.