Submersing Arduino Due in a FPS environment

Hello there. Here one of my next projects using the USB host capabilities of Arduino Due.
I want to add Due to an existent control interface for FPS games. So far, I can control movement data using the 3-DoF (yaw, pitch and roll) with a 6TC tracker and eye wear Wrap 920 (both by Vuzix). My approach for the Due is to connect to it another gyroscope mounted in a toy gun to control the mouse position and a couple of shooting buttons. I don't see too much problem to do it but I need to figure out the best way to 'walk' once immersed in the game. I think and accelerometer can do the job.

I have been thinking about a project like this for Battle Field 3.

The mouse aims the person and the gun, so that is your (turn right or left) and (look up or down). Those functions could be incorporated into the gun possibly. The trigger would be the fire button (left mouse button). Then you need a button for the right mouse button and an encoder to work as the mouse wheel for weapon selections.

For walking, you almost have to have buttons. Perhaps a pedal or two for your feet to hit?

The biggest problem I can see is that for BF3, you need around 12+ buttons not counting the direction arrows. That many buttons will be difficult if you do not want to use a keyboard.