I like the idea of making first-aid a bit more powerful.
I am considering using a ad-hoc system that is still based upon hit points, but when a PC is reduced to hit points that equal his CON, he is starting to take actual physical wounds. Damage above that CON total represents wounds that are easily shrugged off, loss of stamina, etc.
Hit points would heal much faster than the default (1 per hour per level), except when a PC's HP gets below his con. At that point, he can only heal 1hp per day (2hp if tended by someone with healing skill). Once he's back above his CON score, the "fast" healing resumes.
PC's might still get their CON bonus with leveling, since this would represent additional stamina and fortitude through experience and training. However, their basic wound threshold would not change (cept though maybe a feat or some-such).
Therefore, since a cure spell essentially heals from the "bottom up" it would first have an effect on actual physical wounds, and then on merely "refreshing" the character. This resolves the discrepancy with healing a commoner vs. healing a 10th level fighter. Both will actually be similiar in how effective a spell is at healing their wounds.
THe main drawback to this system would be that I need to give additional HP's to 1st level characters (something like their CON score + 1/2 HD). This would make 1st level PC's a bit more powerful, but would balance out at 2nd level and beyond. The system could also be appied to NPC's and monsters, but I don't want to drag low-level combat out. So, that 2hp kobold won't get the benefit of his CON score.
I'm still working out the kinks, but the goal is to have a system which actually incorporates the idea of having a difference between physical wounds and regular hit points, without introducing the complexities of the vitality/wound system. NPC's and creatures can continue to use rudimentary hit points, armor works the same, and critical hits would continue to be applied normally. I also think it will be nice because it will discourage the use of Cleric's as "hit point rechargers" (I want to run a low-magic campaign) and/or the routine of resting for days after every battle. Under this system, the general routine will be to rest for a few minutes or an hour after a strenous combat. If someone gets hit hard and physically wounded, they are going to have to seek some healing.
As a said, pretty ad-hoc, but it is intended to streamline healing without taking away the element of danger.