One of the handholds I'd need is a physics engine which which models a robotic arm down to the finest levels of motor control and feedback. I am not a mechanical engineer, and I do not know where to begin with a problem like that. I don't imagine this is hard to build using existing physics engines, but it wouldn't work out the box. It requires some deep domain knowledge of things like friction, tensile strength, and so on. A system like this would spur progress in robotics immensely.