I'm sorry I do not understand how. How can the thrust be higher than the drag at the wheel? Aren't they are mechanically connected? Move air back at v/2 relative to what, the cart or the ground? If you use gears to make the propeller move faster than the wheels, it will displace more air but also drag the wheels more, because it does more work and needs more energy, if you make it spin slower it provides less acceleration but also causes less drag, at least the way I understand it.