If it works like you describe it would be a good system, I agree. You make good points.

However, AP weapons would rather confuse this issue. I already feel that they are far too effective in EB compared to our historical reports. (Is there any evidence, any ancient source that ascribed victory to an army's use of falcatas instead of gladii?) If armour values were meant as a more generic representation of a unit's melee-capacity, giving every unit with a curved sword or club the ability to halve this value would rather send historical balance flying out of the window.