Good points. It looks like there's also a system on the balance to make sure that the beat, etc aren't knocked out of line by a shock. As to the rotor- a rotor doesn't need to make a full rotation in order to send power to the mainspring- when the rotor rotates it moves gearing throughout its rotation so even if it moves halfway in one direction and then stops and goes the other way, etc with a bi-directional winding system there's still a net benefit.