This is more like a ribbon microphone than anything. Ways to change the output and efficiency:
1) Using super-efficient magnets and coil windings
2) Studies into super light weight and flexible materials ( preferably made out of cheap materials or waste). They would also have to be cleaned easily or not accumulate any residue from climate, or bird crap.
3) Create an auto-tensioner for the membrane that is adjusted by a sensor that detects wind speed. Could be run off a computer that has aggregate wind model data for a region synced to 24 hr. wind speeds.
4) Possible suspending of the magnet in a ferofluid that overcomes the effects of gravity and makes it that much easier for it to travel off miniscule amounts of wind.
5) Possibly using multiple nano-sized motors in an all-in-one module attached to the membrane. Maybe enclosed in a vacuum.
-The best possible thing would for every manufacturer to start making DC power supplies for their products instead of AC. If everyone was using DC instead of AC with the supply coming from their own property, you would not have to worry about transmission losses and distribution. DC would be more efficient. This was the whole debate when AC and DC power were first developed and trying to get public support. The power equivalent of BETA vs. VHS.