What qualities are we talking about? His speed of thought, his ability to see the big picture, his understanding of the aircraft's safety parameters, his reaction time, his awareness of what the rest of the crew require of him, his vigilance, his athleticism, his resilience, his determination, his ability to think on his feet, his coordination, his ability to prioritise, his adaptability, his ability to offload the pilots and fulfil duties on their behalf (eg navigation), the speed of his comprehension, his performance under pressure, his ability to assimilate multiple inputs without reaching saturation point. The list is long and I've only just touched upon it.
Don't forget facing forward and giving clear hand signals.
