You could invest in a cheap LCD which would allow menus.
Search the forums for PS3, PS2 controller support ( it is out there somewhere ).
When you can get the controller talking to the Arduino you can learn how the controller works. Then you can set up the Arduino to talk to the console.
If you can get your hands on a spare controller, you could take it apart and have the Arduino control the actual buttons. This may be easier than trying to get the Arduino to interface the console directly. ( i think this is what you want ).
Check out the button libraries, maybe use a pezio buzzer to sound modes if you don't have an LCD.
There should be ample information in the playground ( link up top left )
If he is able to use his feet, maybe a set of foot pedals or keyboard style interface may be an idea. I would imagine it would be difficult to get a suitable key interface on the back of the controller ( or do you only intend to have the Tactical buttons there? )