the First Officer is to taxi the airplane, the Commander then does...co-pilot duties
If the First Officer is taxiing the aircraft what should the Captain do? There is surely no roll (sic) reversal here as the Captain is always the Captain (unless incapacitated) regardless of who is pilot flying or non flying. By that I mean there might be a change in duties from one sector to the next, which I thought was pretty common in most airlines, but the Captain is the one who ultimately calls the shots.