Apart from removing the camera, there is nothing you can do when operating single pilot. At the moment Airbus do not make aircraft that are designed to be single pilot, the presumption is that 2 crew will be in the cockpit. Of course it is up to the operator what they consider as an acceptable time for one pilot to be alone in the cockpit.
However apart from an incident like this with an external control restriction I find it difficult to imagine anything like this happening. The sidestick has no input when the autopilot is engaged, it is isolated. Mechanically moving the sidestick will disengage the autopilot allowing sidestick inputs. Following disengagement if no movement to the sidestick is made the aircraft maintains it's last attitude (within control law limits.) Although we practice problems with sidestick input in the sim and there are procedures, I don't think they have ever been needed in live operations, although I could be wrong.