Well, you didn't actually ask about encumbrance, now did ya? But since you ask so nicely, here's mine rule for that...
"Encumbrance Capacity: SIZ x (STR + 10) / 20 (x14 lbs). Over half Encumbers: Movement, Initiative & Dex-based skills are x1/2.
Armour Burden (Light/Moderate/Heavy) can affect physical (generally DEX-based) skills, movement rate and magic spell-casting.
Light: no skill penalty, -1 Move, +10% Magic fumble. Moderate: Skills x1/2, -2 Move, +20% Magic fumble. Heavy: Skills x 1/10, -3 Move, +30% Magic fumble. Listen/Spot skills are greatly disadvantaged (x1/10) in Full/Great Helm; Lock-picking, Shooting Bows and Playing Instruments are impossible in Gauntlets. Anyone not trained to the burden of armour is automatically Encumbered."
Not so neat as the Fatigue rule, and I don't usually invoke it. But it's there, just in case anyone tries anything too blatantly unreasonable...