[Saber Cherry]

There's also the possiblity of cumulative armor damage. As in... every hit that lands, regardless of whether it penetrates, has a chance of reducing the opponent's protection by 1. This should be proportional to the strength of the damage roll (str+weapon+2d6). So neither a damage roll of 10 nor a damage roll of 20 would damage a unit with a protection roll of 22, but the damage roll of 20 would be twice as likely to degrade the victim's armor. An attack would probably have (damage roll)% of damaging the armor by 1 point.

The protection reduction would stay for the length of the turn (but be repaired each month). So heavy infantry peppered with slings would take no damage at first, but after 10 rounds of being hit by 5 rocks per person per round, their armor would be badly degraded, and they'd start taking HP damage. Entropy should eventually cause the demise of any highly armored supercombatant=)

Well, that's just a little suggestion I have.