While your idea has merit, I almost feel like you took the concept a bit too far. Near the end of my play, I actually took my hands off the keyboard and just let the game play itself. It seems like you might have been trying to deal with the question "In a game about shooting everything, what's the consequence for randomly firing?" and your answer was "It won't shoot otherwise." This makes logical sense, but doesn't end up being great fun in practice, especially when you start removing the player's locomotive option, hence the keyboard hand removal.
I think this idea is worth exploring, but might need a more subtle touch. A way to steadily remove control from the player without actively disengaging them. If this were my game, that question of "What's the consequence of randomly firing" would be my first consideration.