Ok so I was going over the Armor as DR from UC and I'm having problems with it. While it seems to work alright at lower levels it breaks down at higher levels Most higher level creatures get harder to hit because of Natural Armor rather then from avoiding blows. This means they become crazy easy to hit but almost impossible to damage. Using the Armor as DR rules higher levels of Base Attack Bonus are mostly wasted when stronger mobs aren't much harder to hit then starter mobs.
Let's take the example of a 12th level fighter against a purple worm. He only needs a 4 to hit but has to do over 22 points of damage just to get past the worm's natural armor. Which means he'll pretty much always hit it but never hurt it.
Or look at stone age hunters trying to take down a mastodon. It's pretty well impossible with stone spears. Oh and you can just forget about ever doing any damage to a Tarrasque without spells.
The solution would seem to be to transfer some of the wasted BAB into damage for overcoming DR. A simple (and I believe elegant) way of doing this is to take the amount you beat an enemy's Defense by and add it to your damage roll.
Now Let's look at that fighter against the worm again. Let's say he rolls a 10 plus his BAB of 12 for 22 to hit. The worm has a Defense of 4. So he beat it by 18 which is added to his damage roll. This nicely counters most of the worm's DR of 22 and means he can actually reasonably hurt the damn thing.
Doing more damage against unarmored PCs doesn't seem like a huge issue to me. It actually gives warrior types a little extra edge against casters at higher levels where they start to lag behind casters anyways.
I dunno. Do you guys think this idea would work?