Without having read most of the replies, I'll comment on the original post: If I'm reading this right, one proposal is that, somehow, an attack becomes easier to dodge if it has poison on it?
That is, incurring a penalty to hit because you have to aim for the soft spots means that, somehow, the defender has to expend less energy (read "fatigue") dodging the blow.
That, on the surface, just seems wrong. It presumes, in fact, that the target always knows if a weapon or monster is poisonous.
Hit points have always had a paradox: Presuming that the increase over levels reflects an improved skill at rolling with blows or avoiding them with less effort, we have the paradox that experienced characters get harder to heal. 10 hit points of damage to a 1st level character is a life threatening injury, major body trauma. To duplicate that major body trauma on a 10th level character you'd need to a lot more damage. So, faced with similar levels of trauma, why is one character ten times harder to heal than the other?
D&D 4 tried to address this with Healing Surges, so healing scaled with character levels. Sometimes. (Many healing powers still did fixed numbers of points per healing.) The oddity there was that there was little reason to introduce or use higher powered healing magics. The 1st level ones that could heal a major body trauma at 1st level still work just as well at 10th level.
Treating wounds as a combination of actual trauma and fatigue works out, when dealing with poison, if you take Saves into account. That poisoned dagger that does a D3 of damage, plus poison, leaves a deep cut in a low level character, and thus there is more poison exposure. As the target's hit points go up with levels that same strike is cutting less and less flesh, leaving less poison in the wound and making it easier for them to Save against.
The monkey wrench in the mix comes when you consider targets that have a lot of hit points not because they're nimble or experience at dodging, but just because they're big and tough. Things where, in 3.5 terms, their Flat Footed AC is the same as their full AC. Their HP aren't the result of being experienced fighters or knowing how to minimize the blow, and the poisoned blade strikes deep every time. They may or may not have a good Fortitude/Poison save, regardless of their hit points.
Because their Hit Point/Level/AC/Save structure isn't the same as for a PC race, the rationale for how poison does or doesn't affect them gets harder to justify.
So "Hit points as Fatigue" is a great concept, for PC types who acquire "unnatural" levels of hit points through level advancement, but demands a heavy dose of "suspension of disbelief" when applied to creatures that have a lot of hit points because they're naturally big and tough.
Which brings us back to your "Wand of ignoring inconsistencies".
The sad fact is that HP, as they've always been played, by any rationale, pretty much requires that aforementioned magic item.