Warnings of a bonanza for lawyers are putting pressure on new Labor Secretary Lynn M. Martin. Last year, then-Secretary Elizabeth H. Dole proposed a bill to toughen pension auditing standards and hit violators with stiffer sanctions. Business lobbyists complain that a provision requiring payment of legal fees and expert-witness costs for successful plaintiffs would produce a costly surge in unnecessary litigation. They say judges generally award such payments where merited. Corporations have formed a coalition to persuade Martin to revise the proposals.