There's enough room for an internal female usb port. I did it here (
http://geekhack.org/index.php?topic=45978.0) with a Teensy because I needed to convert from ps2 to usb, but just a female usb port wired directly to the pcb works too. I've done it several times.
Limitations:
- you're limited to the center port (like you mentioned)
- you have to use usb cables with a slim-ish male connector (QFR sized or smaller)
EDIT: if you plan to use the cable kit that sticks out the back, you would need at least 6 inches of cable from the pcb end to the base of the female end to clear the back of the case. Extra length would be ok, because there's enough room inside the case to wind the cable around a few times before exiting the case. Cable width shouldn't be an issue. The channels that hold the cable in place can be cut to make room for wider cables.
