A question: is it good that the secondary effect is always a benefit? Should there be instances where the secondary effect might be less than advantageous, to further add to the element of choice/risk?
I think a secondary effect that was a disadvantage would be very interesting. The biggest change that the game has to make in a future edition (at least according to the system I'm developing at the moment) is to go from a binary resolution system to a ternary resolution system. By having three possible results rather than two, you can really get some funky stuff happening (such as what you suggest above). When I've got my system written up, I'll attach an alpha of the rules here at EN World. I've only been working on it for about 6 years.
Also, Herreman, if you divorce hit points completely from physical damage then what do you replace them with in order to quantify actual physical damage/condition?
Lan-"I'm the secondary effect you didn't want"-efan
Hit Points
In an ideal system (again speaking from the personal ideal I'm currently forging), hit points represent what they have always meant: the capacity to turn a serious blow into a less serious one, luck, endurance, a handful of scratches that stings but nothing that a kiss won't fix, divine providence, inner strength, the will to keep going. Hit points are readily "restored" with a quick break or rest. The beauty is, that you can also "spend" hit points to do particularly exhausting actions or actions that require a special degree of effort.
Wounds
Real physical damage however is represented by wounds which for example are represented numerically by points of damage - a 10 point wound. Without assistance, a wound heals by 1 point every day - so as to define what a point means. And so healing from a wound is slower than restoration of hit points. If the total number of wounds equals a particular amount, then your character is incapacitated which typically means they can't do very much except feel a stack of pain. If the total number of wounds equals or exceeds a further amount, your character is irrevocably dying. It might take them a little while to go but at this point mundane healing (as well as most kinds of divine healing) cannot work. Great for last dying words and so on. Consciousness is a different effect that does not rely on hit points or wounds.
Hit Points and Wounds
The thing that makes the whole thing work is the capacity to transfer wound point damage into hit point loss. In this way, a potential wound is instead a fairly harmless scratch that as hit point loss is easily restored. This is something most can readily achieve in combat. There are instances where the capacity to transfer may be denied (typically with critical hits [soft,standard or hard] and "unavoidable" physical damage) although even then, there are a bunch of things that help protect a character from taking a wound even under the worst circumstances.
By well and truly dividing the two, all the silly conundrums that come up in regards to Schrodinger's cat, healing, the "bloodied" condition and so on are instantly negated, including the need for a party to have a divine healer (although a mundane healer outside of combat helps get the troops back in fighting trim). So yeah... that's what I'm doing.
Best Regards
Herremann the Wise