The guy I know has his rear steer in a joystick type thing he works with his right hand on the consol and it can be locked out.
What I mean is a system like the forklifts that can work entirely from the steering wheel only it can be set to crab or be opposing to turn on a dime, but either way you are working it only with the steering wheel, no extra stick or control. Has this been done on a Toyota?