Even with a skid-steer vehicle (6WD for example) it is straightforward to program a driver interface wherein the vehicle will turn in an arc so as to go in the direction of the joystick angle with a speed proportional to the joystick radius. For example:
http://www.chiefdelphi.com/media/papers/2438
With an omnidirectional drive (like mecanum or omni or swerve), it can be programmed to
immediately go in the direction of the joystick angle while simultaneously rotating to align itself with the direction of travel. Or, with the push of a button, instead go in the direction of the joystick angle without aligning.