utilising the data port for a custom controller conection

[TechDante1]

im planing on building my own gb0 but would like to use a teensy a bit more than just emulate the buttons. i was thinking that if you kept the data connection port off the original game boy circuit board would it have enough pins on it to be able to hook up a couple of controllers so using a hdmi cable and controllers you could run two player on a big screen or single player on the game boy. or would it just be easier to port two of the usb ports from a hub to the outside of case and use two usb controllers??

[Ganreizu]

Why not just get a usb hub for the external usb and use usb controllers from there?