My additions..
I don't know if having the armor absorb all the damage is a good idea... Rather, it should work something like this.
You start out and have armor X which has,
Armor value: Works like current armor, a base amount of reduction capacity.
Weight: Same as current
Hit points: Amount of damage armor can absorb before becoming "minimally effective"
Now, the way that damage reduction will be handled is where the big difference is.
Rather then have the hit points absorb all damage outright it will rather be in place so that you absorb more damage based on how much HP the armor has. So if i have 100% hp armor the armor might absorb 75% of the damage (or something) and then go down to 50% hp... and if i get hit with my armor at 50% let say it only absorbs 25% of the damage. The amount of 'hp lost" could also be effected by the type of damage and weight of weapon.. so if someone hits me with a short sword while im in full plate it may only take away 5% of the armor hp and do to my body only a few damage. With that said, i think the idea that the armor absorbs all of the damage is dumb, because even if you have full plate and i swing a sharp light sword at you as hard as i can it's not going to simply glance off every time so that you feel nothing. Also, the idea the the armor eventually "breaks" and effectively leaves you naked is really dumb, rather this is a way to simulate the armor becoming "damaged"...
But.. these increases in damage reduction are added onto the base armor value... so it effectively keeps armor the way it is now while also adding a small boost for the first few hits..
so the general equation is something along the lines
damage done = (standard crp damage calculation with armor value included) * percent_absorbed, where percent absorbed ranges between .01 and 1 and which has it's value based on the amount of HP in the armor.
The thing to remember here is that what we are basically doing is altering the core mechanics in a significant way by changing the standard number of hits it takes to kill someone. Currently for most of the population it takes 3-4 hits to kill.. The question you want to ask your self is how many more hits do you want it to take to kill someone in armor? I think that the amount of HP and the resistances of the armor should not grow linearly with armor cost... Plate armor should have more HP and more restiances, where as leather armor should have very little hp and weak resistances.
or we could just increase the number of glancing blows on plate?