The spotlight on the alternative mortgage market has shined largely on the origination side in recent months, as analysts and regulators have wrestled with such thorny issues as the long-term performance outlook and the nuts-and-bolts of how loans are marketed, underwritten and sold. The focus on origination is evident in proposed guidance that was issued recently by federal bank and thrift regulators. The regulatory proposal urges lenders to limit their portfolio exposure to nontraditional…