The hedge fund manager is waging his own money this time in a bid to build another financial behemoth that can rival the life's work of Warren Buffett.

A key problem is that the Howard Hughes board and the special committee evaluating the proposal may not want to turn the company into an Ackman-led mini Berkshire.

Bill Ackman's Pershing Square proposed to acquire 10 million newly issued Howard Hughes shares at $90 per share — up from $85 per share earlier.