Not too bad. I too have worked a little on a hit location chart and was going to make a crit chart inspired by Rolemaster.
I'll have to think and look over it better, but you have some idea's here. I like the healing/injury thing. I think if some one had a level 4 injury and and was touched with a level two healing spell I'd reduce the wound to level two. In order for the wound to be reduced any more they'd have to be touched with a level three, or greater healing spell.
If I find my chicken scrathes I pretty much had a hit location chart with modifiers to hit. Various shots could be taken such as low shot, mid shot, high shot, or whatever. I would only bother to find out where some one was hit if it was a critical hit though. Non critical hits are pretty much superficial wounds.
From Rolemaster it seems to be bludgeoning weapons had a greater tendancy to stun opponents and cause breaks of course, slashing weapons got more bonus damage and piercing weapons caused bleeders. I hadn't got that far yet though and currently have a more simplistic, but deadlier combat system than the normal rules.
It involves the possibility of instant death and a variation of the clobbered rules.
If you roll within your critical threat range, but do not actualy get in a critical hit your opponent must mave a fort save or suffer the effects as per the Doom spell for one combat round.
If you actualy get in a critical hit it's a save, or suffer the effects as per the doom spell and reduced to a half phase action on your next action.
If you get a critical threat and your critical hit roll lands within your critical threat range again, called a Death Threat (crit threat range of the weapon for the purposes of Death Threats is only as follows: Improved Crit and Keen only add 1. Therefore a Keen Rapier in the hands of one with improved crit would have a Death Threat range of 15+), the target must make a fort save, or die. Modifiers are present for size of weapon vs size of target. That way Dragons are not likely to die from a dagger strike (unless they roll a save of "1") Even if the target makes the Death Threat save they suffer the effects as per the Doom spell for one round and lose a half phase.
I also include the death from massive damage.
This variation does not require any more dice rolls with the exception of the Fortitude Saves. It means a 10th level fighter getting hit with a critical strike from a kobold throwing a javlin could kill him, but not very likely. At the very least the fighter could be taken back by the painful strike and slowed up for a moment instead of ignoring the hit altogether like Aragorn and Legolas ignoring arrows in Moria.
One more posible addition is that when characters are reduced to half hit points they suffer a -1 to ALL D20 die rolls and when reduced to 1/4 hit points they suffer a -2.
I've looked at several wound/vitality system and although one, or two have been tempting I feel the possibility of death and deadliness can be achieved with out having two sets of hit points and the extra challenges that presents.