Sure, completely possible in theory. That would of course be equivalent of deploying an air brake almost the size of the rotor/propeller disk. So descend rates

Sure, completely possible in theory. That would of course be equivalent of deploying an air brake almost the size of the rotor/propeller disk. So descend rates would be pretty fast, and aerodynamic stability not necessarily guaranteed. In the end you probably have to design the aircraft for it. Might be worth it for applications like sky-diving planes or heli-sking helicopters.