@younata I've been mulling around in my head something like the diesel-electric drive on a locomotive... instead of a big low-rpm direct-drive engine, a small, high-rpm one driving a generator which could charge batteries and/or directly feed a lightweight annular motor... This has the advantage of, instead of a heavy, bulky PSRU in front of a fast-turning engine, your "PSRU" is some fat wires and a flat-plate motor... and you _could_ ditch the 24v generator and just have the big guy and split the power to an avionics battery and the prime mover batteries... or not, go redundant, and have separate buses for safety... No idea how cost-effective this would be.