A group of Tesla Inc. investors wants the electric-car maker’s board to grow up. : A Securities and Exchange Commission settlement that requires Tesla to replace Elon Musk with a new chairman and add two independent directors doesn’t go far enough to fix the company’s corporate governance woes, according to a union-affiliated investor group and officials representing major pension funds in five states. The investors—several of which have pressured Tesla in the past and achieved mixed results—play out a series of measures the board should take to boost oversight and better hold Musk accountable as chief executive officer.