While you were sleeping

I want to add something to the HP rules because it makes sense and is a logical extension of my HP rules.  However I'm worried it might have unintended repercussions to game play.  The HP rules state that if a character's HP drops to 0 they are unconscious and all further damage applies directly to their stats.  When any stat falls to 0 they are in an unresponsive coma and if their STR stat falls to 0 they are dead.  The line I want to change in here is this:

If a character's HP drops to 0 they are unconscious.  When a character is unconscious, sleeping or otherwise unable to react, all damage taken applies directly to their stats.

Your HP are your ability to avoid damage and you can't avoid damage when you are unconscious or unable to react. This doesn't mean just being tied up because you can move and struggle and be tricky even when tied up. In the same vein it wouldn't mean most forms of magical holding or charm because you should be able to resist that. This also wouldn't apply to surprise or things you don't know about, as in a surprise missile attack which you might somehow sense just before it occurs.  But if you are actually unable to react (including mentally cause, hey magic hero fate here!) you maybe shouldn't have hit points apply to the damage.

I think this makes total sense and would avoid the temptation for any weird coup de grâce rules tacked onto the game via in house rules or à la the SRD.  I'm sure someone will use this to beat me over the head with at some point however.