Risk-sharing programs that have already been tested and proven effective could be dusted off and made the focal point of efforts to steer the mortgage finance system to a more sustainable, less volatile foundation, investors say. There is widespread agreement that private capital needs to play a much greater role in the mortgage finance system that has been dominated by Fannie Mae, Freddie Mac and the government mortgage-insurance programs since the financial crisis of 2008. There is no consensus on how to do that, and little likelihood that Congress will agree to a solution any time...