[Brandy]

I've done it that way and like it a lot. We did this:

First aid stabilizes all wounds and restores 1 point to the target, applied to the largest wound.
Supernatural healing (major heal, minor heal, healing advantage) targets a wound, not general HP. (I did add a new spell that heals all wounds at the same time.)
Natural healing heals all wounds at the same time.

The result of this is that in the absence of supernatural healing, 8 1-point wounds heal much faster than 1 8-point wound, and that has always felt right to me.