Something like a 3-position toggle switch that the controller checks the position of. Switch is polled for which position its in, and controller changes kp/ki values depending on position that is read. Have a "safety loop" so that it only changes modes when speed=0.
Position 1: "crawler" setup
Position 2: "normal" setup
Position 3: "I'm-feeling-evil-and-want-to-show-ricer-boy-next-to-me-at-this-light-a-thing-or-two" setup
How's that sound?