ValuJet was reborn as AirTran. Philip Morris rechristened itself Altria. Blackwater became Xe. Would a name change work for beleaguered General Motors? It would mean casting aside a brand that stood for almost a century as a symbol of American industrial might, but some marketing experts say it might be just the thing to help the once-mighty automaker make a fresh start. "If the goal is to try and put this company on a massive diet and just turn it into a smaller car manufacturing operation, I'm not sure there'd be that much harm in rebranding," said Jean-Pierre Dube, a...