If you look at the pictures I posted above, you can see I have done exactly that. I have a switch that engages/disengages the start button.
My thought was such that if I have some numb-nut in my car and we're driving down the road, and they say "what does this button do?" <idiot pushes button> **Horrible Grinding Noise**
Also the start button will not work unless the ignition is in the 'On' position.