Again, to me you are just using a linear scale and obscuring it for no purpose other than added complexity. It still seems to me like minor spells cost less mp (or whatever) in comparison to major spells. Calling out your reserves at a critical moment is something that people already do with a linear scale. I just don't see any difference in what you're describing, other than possible annoying constraints.
I really do think it adds a dynamic that's not present with a linear scale. The problem I see with a single scale is that any recovery mechanism will apply uniformly across that scale, so you can't differentiate levels of injury qualitatively. I'd like to let players recover quickly from minor injuries once they have a chance to catch their breath between fights, to keep the action brisk. However, it's unrealistic to be injured near death over and over and just bounce back to 100% like that.
Think about what this does for the feeling of risk as you're adventuring. When you can heal from anything quickly, all risk is binary -- either it kills you and the game is over, or you move on unscathed. Games rarely present truly deadly threats around every corner; that would make them too difficult, so there are many boring enemies as filler. Like poker, roguelike play can consist of "hours of boredom punctuated by brief moments of extreme terror." Isn't it a problem that it's boring so much of the time? How many stupid deaths are due to the boredom of everyday enemies that present no mortal threat? Wouldn't a game that keeps you on your toes more, be more exciting?
When I fight an acid mound in Brogue, I often have to fight it barehanded and naked to spare my unprotected weapon and armor. Thus weakened and made vulnerable, I often find that the though fight is still basically easy (I'm in little danger of dying), my health gets pretty low by the time I've finished it off. It's a pretty formulaic situation, the results are pretty consistent, and I do it all the time. To me this feels very gamey and artificial, not to mention uninteresting. If those fights carried with them the possibility of lingering injury, I'd have to pay closer attention and work harder to avoid serious injury. An enemy that can't kill you, but can wound you badly, can mean something besides more nutrition lost due to resting up after the fight.
I believe giving the player that longer-term level of risk to manage and mitigate will make for interesting gameplay. I'm feeling interested enough in this to implement it, so I guess it won't have to be an entirely theoretical discussion. I hope you'll give my game a try when I get a version out for download.