God would REALLY have to be pissed at you! Taking your scenario, yes, the car could suddenly ascend at a rapid rate. The safety device is located on the bottom of the car and would probably not sustain any damage from the rapid rate of assent, therefore as soon as the car reversed to start the fatal plunge, the safeties would set and stop any further movement in the downward direction. You, however, would probably bounce off the ceiling and fall to the floor. Back to the scenario, if the cables came off as suggested, what would pull all the elevator equipment down on top of you?

METHINKS THIS WAS TRIED IN SEVERAL MOVIES AND ELEVATOR MEN EVERYWHERE JUST CHUCKLED AS WE WATCHED IT UNFOLD.