We do not need anything so complex. Most of our engines now use a hall effect pick up which requires a small magnet in the compressor nut. If we wrap a coil of wire close to the magnet we have an alternator. I believe that David James engineering tried this with their Cobra Turbojet in the early 90's. Their problem was way too much voltage and RF noise, nothing insurmountable, but do we need it. What is wrong with batteries?
Personally I would sooner see a bleed taken off the compressor to keep my air tanks topped up.
regards,

John.