For ranged characters, was thinking a useful enhancement would be the ability to blunt your own ammo. Something like "your skill using ranged attacks has led to your ability to blunt ammunition for use against creatures resistant to piercing". 1 AP gives you the ability, small investments in the "Repair" skill increase the enchantment level you can blunt... so 1 point in Repair allows you to blunt up to +1's, 5 points would allow up to +5, etc.
Warforged would have no issues with this, as most already invest in Repair; but admittedly, squishies will be annoyed at losing an AP and some skill points. Though for use where it really matters (low levels), you'd really only need to invest like 3-4 points.