A Washington-based lender, MILA, Inc., has beefed up its nonprime and Alt A programs with the launch of a 40-year mortgage product. One of the key questions confronting lenders seeking to roll out extended amortization products is how those loans should be structured. With regard to the 40-year mortgage, most lenders so far have opted for a structure that includes a balloon payment at the 30-year mark. Others, however, have crafted loans that amortize…