Senate Republicans led by Richard Shelby are drafting an alternative to financial-regulation legislation that Senator Christopher Dodd is developing after bipartisan talks collapsed this month, two Shelby aides said. Shelby’s plan will likely aim to create a consumer protection unit within a new bank regulator instead of the standalone agency sought by Dodd and President Barack Obama, said the aides, who requested anonymity because the talks are private. It would shield taxpayers from costs of unwinding systemically important failed financial firms, the aides said.