Personally I would use a mini-USB to a female USB cable. As you stated this will allow you to use other USB devices on the system (i.e. harddrives, thumb drives, other phones, etc.).
The length probably will not be over 10 feet. My suggestion though is to have your female-type USB connection inside the center console. The only problem is that I did not measure the cables or the distance from the unit jack to the center console hole. For that measurement take a piece of string and run it from the center speaker down to the glovebox then down the side of the center console and then up to the top of the storage box (center console compartment). Of course then you measure the string.
The length probably will not be over 10 feet. My suggestion though is to have your female-type USB connection inside the center console. The only problem is that I did not measure the cables or the distance from the unit jack to the center console hole. For that measurement take a piece of string and run it from the center speaker down to the glovebox then down the side of the center console and then up to the top of the storage box (center console compartment). Of course then you measure the string.