As an artist and now a developer, I have had to deal with this question many MANY times. If I had my choice, I wouldn’t have a pilot at all, but its not about what I want, but what the customer wants.
I personally will never have pilots, copilots, or passengers in the aircraft for VC for MANY reasons.
#1, visibility. As a pilot in FSX, you need to have visual access to every nook and cranny since they hide buttons EVERYWHERE. I know that there are ways around it like camera's and views, but having a user constantly having to think of ways around your artwork means your art is getting in the way. Not something I like.
#2, Seatbelts. I know it sounds like a small thing, but its a real PAIN to model fabric seatbelts, and a harness? UGH! Gives me fits to even think about.
#3, Animation. Its really hard to rig up a pilots arms and legs, but we do it for the external model. We CAN keep it for the internal model, but that leaves #4
#4, Continuity. This one is hard to explain. Basically the pilots hands would be locked to the stick the entire time. So when YOU are adjusting the throttle, the PILOT does not. His hands are still on the stick, yet the throttle moves? Thats braking continuity. Your no longer the pilot, and a ghost is moving the throttle. It would be cool to animate something that the pilots hands reach for whatever your doing, but its almost impossible and would suffer from lag. It takes time to animate the pilots hands moving from the stick too the throttle. Since we cant predict your throttle commands, the throttle will move BEFORE his hands get there. Also, what if the switch is out of reach? Do we have him lean over? Maybe a co-pilot do it? It will take more time to animate pilots and copilots then modeling the ENTIRE AIRCRAFT. That would DOUBLE the price of a product EASY.
#5, Head. If you see your body, and your in the head, what do you do for the neck when you look down? This is why FPS games DONT HAVE BODY's! If the user looks down far enough, he will see into his own neck. Do we have a body with no neck? Or maybe just a bloody stump? There is no answer to this, so every game has left the body out.
Ultimately, there are just WAY TOO MANY PROBLEMS introduced with the addition of pilot/copilot models in the VC. Its just too much work for very little return. Something like A2A's Cub is cool since the female passanger is mostly out of the way, but other then that, I stay away from pilots in VC.
Just my professional opinion.
P.S. I almost forgot an important one! Performance! VS's are VERY complex, and so are PEOPLE. To have both would kill frame rate.