The DM who originally introduced me to D&D came up with this idea a number of years ago. On the surface, it sounds a bit complicated, but in practice it works amazingly well.
The Basic Idea
There are a number of healing spells: Cure Light Wounds, Cure Serious Wounds, Cure Critical Wounds, and Heal. They each heal a different amount of damage but otherwise are fairly interchangeable. Instead of casting a powerful healing spell, you could cast a number of lesser healing spells and achieve the same result. Outside of combat, this devalues the more powerful healing spells.
What we implemented was a limit on what wounds each spell could affect. Cure Light Wounds can still heal the same number of hit points, but it cannot affect any wounds greater than 10 hit points. Cure Serious Wounds is limited to wounds up to 20 hit points and Cure Critical Wounds is limited to wounds up to 40 hit points. Wounds greater than 40 hit points require a Heal spell.
The largest wound (that the spell can affect) is healed first. If the spell’s healing power is not used up on that wound, the next largest is affected, and so on.
How It Works In Practice
First off, each wound must be recorded separately. This may seem like it would turn into a great deal of record keeping but it really is a non issue. Instead of keeping a running total, simply write down “-5″ when you get hit for five points of damage.
We have always used index cards (in addition to character sheets) to track AC, HPs, wounds, mana, etc. That makes it easy to simply hand the healer your index card after the battle so he/she can handle the healing. The healer performs healing, erases or reduces wounds, and returns the index card.
Clearly, this isn’t a game-changing house rule but it does make the higher level healing spells a bit more significant. It also emphasizes the difference between a bunch of minor scratches and a more substantial wound.
Taking It Further
One extension of this rule that we talked about but never implemented was to allow natural healing to heal 1 HP to every wound. If a character has ten 5 HP wounds, each wound would heal 1 HP for a total of 10 HPs of natural healing. If another character has but a single wound for 50 HP, that character would receive a total of 1 HP of natural healing. The rationale being that a bunch of scratches would heal faster than one massive wound.
Another change we discussed but never used was limiting the various healing spells to 10%, 25%, and 50% of the target character’s hit points. Although there are some good arguments for this, we felt that a static hit point limit would be far less complicated.