Rules-lite wound system

The debate over hit points, what they are and what they aren't, has been hashed out pretty thoroughly already.  Luck, combat skill, divine favor, whatever the explanation by which you care to rationalize it, the generally accepted bottom line is that hit points are far more representative of the ability to avoid bodily harm than the actual capacity of the body to soak up damage.  A character with 24 hp can't survive being run through three times with a long sword.  Through one of those factors noted above, or a combination of them, he evades the brunt of attacks that get past his defenses to seriously threaten him, sustaining only superficial hurt to his body but depleting his reserves of stamina, confidence, the favor of the gods, or what-have-you.  Only when those reserves are used up do the blows start connecting for real, rending flesh and breaking bones.

In the rules as written - whether you personally consider it a feature or a bug - a character's health is binary in nature.  Either a character is dead or alive.  A character with 1 hp left functions in all ways but one exactly as he would at full hp.  The next hit in combat will kill him, but until that happens, his ability to hit and damage, and to walk, run, jump, swim, climb, think, carry weight, talk, use class skills, and so on and so forth, is completely unhindered.  To put it in a nutshell, the game doesn't attempt to model any of the effects we might expect from being wounded.  Given the abstract nature of hit points, we can't even say for sure whether the character who takes damage has been wounded, until he's wounded to the death.

Here's a little system I've been working on to add some verisimilitude, tension, and drama to the game, by attempting to simulate injuries within the framework of hit points.  It bears some similarities to other systems I've seen that calculate a "wound threshold" based on a percentage of a character's hit points, but hopefully this is both easier to apply and a better model.  Rather than using a table for hit locations and applying specific effects, this system abstracts the effects of wounds.  It assumes that a penalty to attack may result just as easily from being unable to bear weight on an injured leg as from an injury to the sword arm, and a penalty to movement may result from the pain of a body wound as well as from a leg or foot wound.  If one were so inclined, it would be relatively simple to draw up a hit location chart and apply specific effects according to which body part is wounded, but the abstract way is enough for my purposes.

The basic rule is this:  Any single attack that does damage equal to or greater than 1/4 of a character's current hit points will inflict a wound that hinders his or her ability to move, fight, and function.

An attack that does between 1/4 and 1/2 of the target's current hit points in damage inflicts a light wound. Such a wound imposes a -1 penalty to the character's attack rolls, saving throws, and ability checks, but not damage rolls.  Light wounds heal naturally by resting (i.e. no travel, combat, or other strenuous activity) for 1d6+3 days.  If desired, this may be adjusted by the character's Constitution bonus or penalty.

An attack that does between 1/2 and 3/4 of the target's current hit points in damage inflicts a serious wound. Attack rolls, saving throws, and ability checks are impaired by -2; armor class and damage rolls are reduced by 1 point.  Movement is reduced by half. The wound will heal naturally.  During the first 1d6+3 days of rest, the wound is reduced to a light wound.  It takes another 1d4 weeks of rest for the lingering effects to disappear.  If not healed by magic, a serious wound will likely leave behind a prominent scar.  Left untreated, serious wounds easily become infected and may lead to death or loss of a limb.

An attack that does 3/4 or more of the target's current hit points in damage, without reducing it to 0 or below, inflicts a critical wound.  Attack rolls, saves, and ability checks suffer a -4 penalty, and AC and damage rolls are reduced by 2 points. Movement is reduced by two thirds, rounded up.  Without expert or magical assistance, critical wounds are almost certain to develop infections or other complications.  Critical wounds will heal naturally, but maybe not fully.  In 1d6+3 days under the care of a healer or herbalist, the wound is effectively reduced to a serious wound.  After an additional 1d4 weeks of rest, a saving throw vs. death ray must be made; if successful, the wound is reduced to a light wound.  In another 2d4 weeks, a second save is attempted, and if successful the remaining light wound effects heal and the character makes a full recovery.  If either save is failed, the character is permanently disabled, retaining the penalties of either a serious wound or a light wound.  

Wound effects are cumulative if the character should sustain more than one wound.

Magical healing spells may be used to cure wounds in addition to restoring hit points.  Each use of a spell affects only one wound, so a character who has sustained multiple wounds will need multiple healing spells.  A cure light wounds spell or equivalent will reduced the severity of a wound by one level (light to none, serious to light, critical to serious.)  A cure serious wounds spell reduces severity by two levels, and a cure critical wounds spell reduces it by three levels, i.e. it will completely heal any one wound.   A cureall spell will simultaneously heal all wounds suffered by the target of the spell. 

Only one form of magical healing applies to any given wound.  A second spell used on the same wound will supersede the first if it is more powerful, but they do not stack.  For example:  A character suffers a critical wound.  The party's cleric casts a cure light wounds spell, reducing it by one wound level to a serious wound.  A second cure light wounds spell will have no further effect, except to restore more hit points.  If the cleric later casts a cure serious wounds spell, it reduces the original wound by two steps, to a light wound.

One of the things I like about this system, at least in theory, is that as a character is worn down in combat, it becomes progressively more likely that any given hit will wound him, whereas with a wound threshold based on a percentage of total hit points it's equally easy or difficult to inflict a wound at any point in battle.  I think using a percentage of current hit points rather than total is more in keeping with hp as ability to avoid injury.

This is yet another of those things I'm going to be play testing soon, but as yet its purely a theoretical system, and any input is welcome.

Bonus:  How about  new cleric spell especially for the system?

Soothe
Level 1
Range: Touch
Duration:  1 hour
Effect:  One creature

This spell reduces pain in the target creature.  For the duration of the spell, all of the recipient's wounds are treated as if one level lower than they actually are, including wounds sustained after the spell has been cast.  Thus, a character suffering the effects of two light wounds and one serious wound functions as if suffering from only one light wound.  Any further wounds sustained during the spell's duration are also treated as one level lower; thus new light wounds have no effect until it expires, new serious wounds are treated as light, and new critical wounds are treated as serious.  If the recipient engages in any strenuous activity during the spell's duration, when it expires he or she must make a saving throw vs. death ray or suffer 1d8 points of damage due to aggravating injuries.  If cast on an uninjured creature, and no wounds are inflicted while the spell is in effect, no saving throw is necessary and no damage is incurred.