Back to the topic of co-pilots, another aspect of that guy in the side-seat could be modeled: Stick forces.
The co-pilot didn't just spend the whole flight sitting there, picking his nose, watching the gages, and playing 'spare pilot' if need be, he also helped with controling the plane, as hydraulic assist wasn't all that common back then.
How about, in addition to having that 'spare pilot', you also have it so that if one of the flight-deck crew is knocked out, the controls become stiffer, to simulate the extra work load one guy has to go through to fly one of those big planes.