Knocking a Character Unconscious

Hello again, everyone. I've been talking to Grumbleshanks about better ways of handling lethal vs. nonlethal damage, and I think I've come up with a better system. Here it is. If you have any questions, comments, or concerns, please let me know.

Rules for Lethal and Nonlethal Damage:

• If you are attempting to deal nonlethal damage with a lethal weapon or vice versa, you take a -4 penalty to attack, as you try to carefully use the weapon for something it wasn't intended.
• When nonlethal damage is dealt, it stacks with the lethal damage that has already been received. 
• Example: If you receive a nonlethal punch in the face after being stabbed repeatedly, you may pass out from the combination.
• When lethal damage is dealt, it does not stack with the nonlethal damage that has been received.
• Example: If you have been punched in the face and are near unconsciousness, and then someone stabs you, you are not that close to dying from the one stab wound.
• In order to make an enemy pass out, the blow that puts them over the edge has to be a nonlethal blow. (You can't make a character pass out from lethal blows.)