Seems like an awful lot of fiddling to achieve something for a low magic campaign you could probably just achieve more simply.
If you want to make lighter armours more attractive:
In medium armour any skill bonus' & Dex mods are capped at +1.
In heavy armour, no skill bonus' to physical tasks, no positive dex mods & rolls of 1 on checks for climbing, swimming etc are interpreted as disastrous.
If you still want the HP stuff.
Begin play with 6 Wounds + 1 class HD roll.
The initial 6 represents Wounds/Meat. And any dmg sustained to Wounds/Meat takes 1 week per pt to heal.
Any HP dmg sustained above the Wounds total just heal to full with a good nights rest.
Option B: for encouraging non armoured characters. The Naked Barbarian Rule: barbarians can use their Con/Str/CHa (pick whichever suits your mental map of barbarians) as their AC score. Stacks with a shield but not other armours.