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This is a whole lot of hand-wringing and mental gymnastics over a concept that is relatively simple. There are basically 5 forces relevant to the plane as it tries to take off: thrust, drag, lift, weight, and some kind of friction or friction-like resistance to motion as a result of the plane's contact with the ground.
Thrust and weight are completely unaffected by whether the plane is on a treadmill or not. Lift and drag are based entirely on the motion of the plane relative to the air, so the question is really about whether the plane can achieve the required airspeed given a set of initial conditions and in opposite to whatever friction-like force exists between it and the ground. The friction force will depend on the motion of the plane relative to the ground. Let's ignore thrust and weight since they don't change. The problem boils down to a question of whether the aircraft can achieve and airspeed fast enough to generate lift greater than its weight. That means the lift requirement (and thus the airspeed and drag) do not change, and this is only a question of whether the friction force is great enough to prevent reaching that target airspeed.
Regarding the motion of the plane relative to the air, that depends on the motion relative to the ground in two ways: the initial airspeed (if the plane is initially moving with the moving ground) and the maximum achievable airspeed (since the friction force will be larger for larger motion relative to the ground, it essentially creates some terminal velocity). The initial velocity is essentially irrelevant to the final velocity and will only affect how long it takes to reach that terminal velocity, which must be greater than the airspeed required for takeoff.
That leaves us with the effect of friction with the ground. Typically, the thrust only has to overcome drag and rolling friction due to the wheels. If the ground is a treadmill opposing this motion, the only change is that the wheels are now turning faster, so there is likely to be more rolling friction. However, rolling friction is going to be incredibly tiny compared to the drag force and the thrust force as to be effectively irrelevant to the problem. This seems to be confirmed by that full-scale Mythbusters video I posted earlier. With pontoons on a seaplane, the situation is quite a bit more difficult because viscous drag on a pontoon from water is going to be much higher than rolling friction. It is conceivable that there could be a water velocity that is high enough that this drag is large enough, when combined with drag from the air, to prevent a plane from reaching takeoff velocity. I really can't think of a realistic scenario where this would be true of wheels.
Thrust and weight are completely unaffected by whether the plane is on a treadmill or not. Lift and drag are based entirely on the motion of the plane relative to the air, so the question is really about whether the plane can achieve the required airspeed given a set of initial conditions and in opposite to whatever friction-like force exists between it and the ground. The friction force will depend on the motion of the plane relative to the ground. Let's ignore thrust and weight since they don't change. The problem boils down to a question of whether the aircraft can achieve and airspeed fast enough to generate lift greater than its weight. That means the lift requirement (and thus the airspeed and drag) do not change, and this is only a question of whether the friction force is great enough to prevent reaching that target airspeed.
Regarding the motion of the plane relative to the air, that depends on the motion relative to the ground in two ways: the initial airspeed (if the plane is initially moving with the moving ground) and the maximum achievable airspeed (since the friction force will be larger for larger motion relative to the ground, it essentially creates some terminal velocity). The initial velocity is essentially irrelevant to the final velocity and will only affect how long it takes to reach that terminal velocity, which must be greater than the airspeed required for takeoff.
That leaves us with the effect of friction with the ground. Typically, the thrust only has to overcome drag and rolling friction due to the wheels. If the ground is a treadmill opposing this motion, the only change is that the wheels are now turning faster, so there is likely to be more rolling friction. However, rolling friction is going to be incredibly tiny compared to the drag force and the thrust force as to be effectively irrelevant to the problem. This seems to be confirmed by that full-scale Mythbusters video I posted earlier. With pontoons on a seaplane, the situation is quite a bit more difficult because viscous drag on a pontoon from water is going to be much higher than rolling friction. It is conceivable that there could be a water velocity that is high enough that this drag is large enough, when combined with drag from the air, to prevent a plane from reaching takeoff velocity. I really can't think of a realistic scenario where this would be true of wheels.