Adjustable-rate mortgages that offer borrowers flexible payment options have become one of the hottest new products on the mortgage landscape. But so far, at least, some large non-prime lenders have decided to sit on the sidelines. A fast-growing product designed to help borrowers cope with skyrocketing home prices, option ARMs allow borrowers to choose among a number of amortization schemes on a monthly basis. The products are being pitched largely to borrowers with good…