This might make sense if one does a lot of business at smaller facilities without adequate ground handling equipment. I think some military aircraft have such systems for such purposes.
But you'd be paying a weight penalty for the life of the aircraft in increased fuel consumption. If the fuel consumed taxiing was a significant issue, I'd expect to see procedures developed where aircraft are hauled out just short of the runway by a tug. The crew could start engines and take care of some stuff while the tug driver drives them out. But all I've ever seen is tugs used to back the a/c away from the gate or haul them away for maintenance.