I came up with this after reading through Ultimate Combat (AWESOMENESS INCARNATE!) and not finding an official one.
I loved the gunslinger, and the gun rules, and i love the armor as DR rules, however, i do think that unarmored warriors should get a treatment as well (not MONK style).
this system was designed to be used in conjunction with the Defense variant and the Armor as DR variant in Ultimate Combat. It is based on a character's armor proficiences. The defense bonus granted is effective against touch attacks. The defense bonus is based on character level and armor proficiencies, so it doesn't matter what classes you have when determining your defense bonus.
Character Level: 1/2/3/4/5/6/7/8/9/10/11/12/14/14/15/16/17/18/19/20
No Armor Prof: +0/+0/+1/+1/+1/+2/+2/+2/+3/+3/+3/+4/+4/+4/+5/+5/+5/+6/+6/+6
Light Armor: +1/+1/+2/+2/+2/+3/+3/+3/+4/+4/+4/+5/+5/+5/+6/+6/+6/+7/+7/+7
Light,Medium:+2/+2/+3/+3/+3/+4/+4/+4/+5/+5/+5/+6/+6/+6/+7/+7/+7/+8/+8/+8
Lgt,Med,Hvy: +3/+3/+4/+4/+4/+5/+5/+5/+6/+6/+6/+7/+7/+7/+8/+8/+8/+9/+9/+9
I modified the system a bit.
what I do is I add the Max dex of the armor to the armor check penalty, and if the result is a negative number, I apply the result as a penalty to the defense bonus granted. if the result is a positive number, no bonus or penalty is subtracted.
Thus, if Joe wants to wear full plate, he would add max dex of +1 to armor check penalty -6, resulting in a -5 penalty to his defense bonus.
If joe wanted to wear a Mithral Breastplate, his max dex would be +5, and armor check penalty would be +0, so he wouldn't get a penalty to the listed defense bonus.
I'm also considering some feats, for example:
Armored Combatant (Combat)
Benefit: When wearing a armor, you may halve the penalty the armor incurs to your defense bonus.
so, in the above example, if Joe wanted to wear full plate, he would take 5, and divide by 2, result 2.5, and rounding down, gives us a -2 penalty to the defense bonus.
and possibly
Improved Armored Combatant
Prerequisite: Armored Combatant, Base Attack Bonus +6
Benefit: When wearing armor, you no longer suffer a penalty to your defense bonus.
just a few thoughts.