The problem with transfering it to the armour is that it's effected by AP weapons which drasticly changes a number of intended balances.

Any foot unit with a sheild giving 6 defence, (most of the dedicated CC units), will suffer a 3 point defence drop against AP attacks, thats quite a big drop and will defintly mess stuff up IMO. It also has big implications for raking fire and HA firing from the rear.

Really we can't come up with a solution that works and dosen't mess up the Auto-Calc ourselves. I've come to the conclusion you can't have a working Auto-Calc whilst still having everything balanced.