Carbon fiber can block radio signals, plus making a "base" out of it would be a mistake for a lot of reasons. The Phantom definitely benefits from a larger footprint. It would be better to attach some skids to the landing gear. I made mine out of 1/4" styrene tubes to help against tip-overs and to raise ground clearance a little. I could extend them only about 1 to 1.25" in the front and keep them out of the camera's view, but that's enough to make a noticeable improvement. You could do something similar out of plastic, wood dowels or even carbon fiber.
There are also a number of after market landing gears that would accomplish the same.