Ungrounded Lightning Rod,
Under some very limiting conditions you may be right.
Here people talk about 0.7 INCHES of air gap between magnets and stator on the larger machines.
To do what I said will cause the stator to be a little thicker, NOT 0.7 inches worth.
The wind gen will supply X power, take it out 12v or 48v, the power taken will be limited to what the wind can supply. This is what matching the blade to the generator is all about, and adjusting the air gap.
Over all less wire is needed if the 12v and 48v share.
Wire thickness ratios will control how much power is delivered to the 12v and 48v sections.
Else the turns ratios can help push more power to one or the other.
Dual voltage solution allows both battery systems to charge at the same time and use standard controllers. Some benefit could be had by modifying the 12v controller (to work like solar controller) and only load dumping with 48v system. (simpler!)
Before I would even consider 4 sets of coils, I would make a transformer to step down the 12v.
The controller to make 4 sets of coils work, would be interesting, must switch configurations to produce 12v or 48v, switching only when the wind is not blowing, else will have problems like star to delta and back systems. Switching systems are not used here for a reason.
Have fun,
Scott.