Debtor countries may postpone the inevitable by borrowing from the IMF or U.S. Treasury to buy out bondholders. This saves the latter from taking a loss - leaving the debtor country with debts that are even harder to annul, because they are to foreign governments and international institutions.
The aim of promoting low down payments is to push prices back up so that fewer houses are going to be in negative equity and fewer people are going to walk away from the mortgages. That will save the from taking a loss on their junk mortgage loans.
To save the banks from making losses that would wipe out their net worth, you'll have to get rid of Social Security. It means that you'll essentially have to abolish government and turn it over to the banking system to run, with an idea that the role of governments is to extract income from the economy to pay to the bondholders and the banks.
