If you are willing to do that, you could probably just switch the potentiometer for an spdt switch like the ones used in nerf blasters normally. I've never tried it, but it might work. Someone should be able to back me up (or not) on this.
The only problem with this is that if I replace the potentiometer with a button, the ESC's have a saftey that will prevent the motors from spinning up. The ESC's need a pulse that tells them to increase the motor's rpm incrementally rather then a signal telling them to increase the motors to full rpm all of a sudden. For example, if you plug in a lipos to a power system of an rc plane or quadcopter etc, and you bind the transmitter and receiver with the throttle stick at a position besides zero throttle, the motors will not spin up to prevent any accidents. Sorry for my bad sentence structure and grammar as it's midnight and I'm tired.