Winston:
Your idea, basically, is not sound, because, though the power harvested is to the cube of the wind speed the, RPM does not follow such factor.
Do you know the RPM factor ?.
Turning ON or OFF a number of coils makes the mill too complicated electronically and this group seems to have an aversion to electronic components.
This aversion could be caused by many factors, from not understanding how the Electrons run in the wire, or lack of experience, or what ever one may think.
The simplest the mill is best it is, I think, it is the general point of view.
Same reason why no one in this group really wants to make a Pitch Controlled hub, ( one or two exceptions).
Nando