As chairman and CEO of investment bank Cantor Fitzgerald and BGC Partners, Howard Lutnick has led a company that grown rapidly. He is even entertaining a future run for mayor, according to the New York Post. Mr. Lutnick's latest move – a bold strike to take over Cantor's rival brokerage, GFI Group – might be his most audacious yet. But will it succeed? A deeper look reveals higher hurdles than have been previously disclosed.