I don’t know if you already have an armor system ready, but if we are not going to use thac0 I had some basic thoughts on armor and a possible system.
The simplest thing to do with armor would probably just be to have each point of armor represent an actual amount of damage reduction, maybe .1% damage reduction per point of armor, so that you basically end up getting 1% damage reduction per 10 armor. You could put tiers on certain armor values to make sure low levels were not being gifted insane armor and just plowing through the low level areas taking no damage.
It might be cool if some weapons and armor had inherent values, like a Reinforced Titanium Breastplate (50) might give you a bonus like -10% damage from enemy vital strikes or something on top of the 5% damage reduction. Or kind of like how my cousin suggested with weapons, you may be able to make classes of armor, heavy, medium, light or something.
I was thinking to make it more desirable to use shields when tanking as opposed to two handing or dual wielding, shields should be pretty beefy to increase the motivation to use them and to offset the loss of damage from not using a two hander. So if you got a shield that was around the same tier as that Reinforced Titanium Breastplate (50), the Reinforced Titanium Shield might be (200) and give you a flat block value of 10 damage as well. So you would end up with 20% damage reduction and then block an addition 10 off of that, after the % reduction is factored.
Monks would just have to be adjusted so that their scaling was on par with armor, and since they don’t use shields, perhaps we could add something to their robes to compensate for the damage reduction from the flat block damage of the shield. Maybe their chi absorbs a flat damage amount while they have robes equipped or something of that nature.