I've thought about it too but surely you would run into problems with the viscosity of the air being the same for both model and full size ship. Whether you could offset this by spinning the rotor more quickly I don't know, and presumably the comparative 'smoothness' of the model rotor surface as opposed to the full size one would have an effect too.
You would have to test in scale wind conditions too which would mean no more than a gentle breeze. Still, it would be interesting to make up a model test rig where you could vary the motor speed and maybe the friction on the rotor surface.
Colin