Tgrendl,
Your thought experiment is a good one, and clearly illustrates the issue. However, the settling you describe is caused by the aircraft running into the ground vortex created by its main rotor wash. In a steady, no wind hover, the rotorwash spreads outward evenly in all directions, at about 8 to 12 knots on average, as a thin sheet close to the ground. On takeoff, the aircraft moves into this outward spreading air, and it causes the air ahead to roll up and interact with the forward part of the rotor disk. This causes a loss of efficiency, and thus the settling. It also causes the lateral stick shift and the ruffling prior to ETL.
A great paper was prepared by a Boeing team during their development of their YUH-61A UTTAS (the one that lost to the Black Hawk) which defined this effect.
In any case, that interchange between the aircraft and its wake takes place up wind, down wind and even in sideward flight.
In the case you describe, the only difference between the still air aircraft and the up wind or downwind aircraft is the speed at which the ground is moving. All the aerodynamics stays the same.
The power to land downwind is exactly the same as the power to land in still air. The negative point is that you did not gain the power that is inherent in landing up wind, where you never have to make your aircraft slow down below windspeed.