Hoping to smooth the way for its proposed acquisition of Dime Bancorp, Washington Mutual has jumped on the best practices bandwagon and announced a huge new affordable-housing pledge. In a statement released last week, the thrift giant said it plans to avoid the referral problems that have plagued other subprime lenders by making its full array of products available at both its prime and subprime outlets. That initiative includes the implementation of a risk-based pricing