IndyMac, the California bank seized by the Federal Deposit Insurance Corp., has given about 4,000 borrowers more affordable mortgages so far. By this weekend, the bank expected to have sent out more than 15,000 modification offers to borrowers, who are saving $430 a month on average. IndyMac’s efforts, which are designed to save the FDIC money by curbing losses on foreclosed homes, are being closely watched nationwide. In fact, Bank of America is taking a similar approach with newly acquired Countrywide Financial as part of an $8.4 billion, 12-state legal settlement reached this month. And now some congressional Democrats and state officials say the FDIC’s approach should be replicated as the Treasury Department buys billions in troubled mortgage debt as part of a $700 billion financial industry bailout.