Forewarned, I haven't attempted to use this mechanic at my gaming table yet.
Currently, the mode of armor in the game is damage reduction. On a successful attack damage is rolled. Yet, before it is deducted from the targets durability the value of the armor is deducted from the damage. Yet, before that the value of the armor piercing is deducted from the armor. These are a lot of values to juggle in the middle of initiative. I understand there is a precedent for it in game like Shadowrun, but it can be cumbersome.
May I recommend a hit threshold model instead? In this mode, when an attack is made the value of the roll is compared to the armor rating of the target, using 30 as the maximum armor value that player characters may achieve. In this first version I would say that if the armor value is greater than the attack value then the attack fails, but I'm not sure if that is the best resolution. Armor piercing then becomes a simpler matter of reducing the minimum success required to land a blow. As a balance, the armor encumbrance is calculated by making the target's armor value a negative penalty to Fray tests, or perhaps a minimum success required on Fray tests.
Weapon damage would have to be recalculated to account for the change. Called shots for armor bypass as it was known in 1st ed would be rather moot. This mechanic has a certain verisimilitude as glancing shots (low rolls under the weapon skill value) are deflected by the armor while shots with a MoS greater than the armor value go through.
EDIT: It occurred to me that an armor defeating called shot would just mean that lower valued success would penetrate the armor. Where normally a target with an armor value of 16 means that the attacker needs to roll over 16 and under their skill, an armor defeating called shot means that any success under the skill would result in a successful attack.
I'll let everyone know more after I playtest the idea some.