That thought that has crossed my mind a few times. I would take a utility box or something of the like and use an arduino and a couple of waterproof buttons on mine though...
Find a program that can assign keystrokes to the gamepad. Jog X-, X+, Y+, X- is crtl+left arrow, right arrow, up arrow, and down arrow respectively.
That should be easy enough to assign to a D Pad so your average guy can figure the arrows on the dpad out.
If you assign an A/B switch combo or similiar to just up arrow and down arrow, you can then change the speed of your jogs as well. (very critical for 0 alignment)
The only issue that I can see is that in order to get to jog, you have to click into the jog tab and highlight the jog speed dropdown in order for these controls to work.
But on another note, the Jog Y+,Y- buttons could also be used during cutting to change feed rate speed manually.
All of these thoughts have been negated by the fact that my computer sits right next to the table on a pivoting arm I built that hangs off the water tank.
Sorry older post, just wanted to share my thoughts.