These are interesting ideas, but as others said, it may need a lot of calculation. Have you thought about using a system similar to weapon breakage (in RMSS)? Depending on the type and quality of the armour, when the attacker makes his roll, if it is a double (11, 22, 33, etc.), you re-roll to see if the armour is damaged.
This could work for me, but I don't want the added complexity. As the Breakage rules, you're trying to bust 100 to save. Adding magical/quality bonus and maybe the bonus from low Difficulty (Leather breast plate vs crush could be Routine +30) or high Difficulty (Longbow arrows vs chain?).
The number of Breakages that armor can withstand could be the AT....
However you run it, if you determine the armor has been damaged, now what?
Do you modify DB, AT, Maneuvering Penalty((
)...
Changing AT might be a first reaction, but would it be accurate? Of course we'd skip AT 12, 11, 4, 3. But damaging AT9 Leather breastplate shouldn't drop you down to a AT8 Hide Coat. Damaging a AT17 Metal Breastplate couldn't drop the AT15 to Full Chain. Should it go from AT17 to AT13 to AT9?
Or could you give a penalty to DB?
Armor that's been banged up may not fit the same. There's a rivet sticking in my side or the gauntlet is sliding off a bit. Changing Maneuver Penalties or Exhaustion rules (whatever those are
) could help.
For me, the question is,
Should damaging armor represent that you're easier to hit or that you're easier to damage?
We also don't use Exhaustion or PP Exhaustion for that matter. Why penalize twice for (effectively) the same thing? Semi-caster's have it bad enough as it is.