Right, but you need a certain amount of forward speed relative to descent to maintain that AoA (assuming you want to maintain a fairly gradual, level descent; m

Right, but you need a certain amount of forward speed relative to descent to maintain that AoA (assuming you want to maintain a fairly gradual, level descent; most passengers would find a steep nose-down descent alarming). If you scrub off all your forward speed by turning your propeller/fan into a generator to charge the batteries, you have to push the nose down to maintain AoA.