I just got done making an alternate weapon and armor sheet that can be printed out in which I did away with the light/heavy distinction entirely. The way I have it there are three "armour" items. I have "helm" which uses the thimble image from the heavy armor and offers 1def and has three usage. I have "armour" which is the light armor image minus the shield (I copied and flipped the exposed part to make a symmetrical armour image that I liked). It also has 3 uses and offers 1 def. Then I have a "shield" which is just the button from the light armor image. It has no usage and gives no def but works differently. Basically, if you have a shield equipped you can declare that you are sacrificing your shield to negate one enemy attack and then it shatters. Each of these items takes up one equipment slot. Occupations that start with light armor get the armor and shield. Occupations that start with heavy armor get all three. I have attached a jpeg of the alternate sheet.
That works I suppose. Why not give the shield three uses though? It's not like it's that fragile.
It's actually not my own rule. In the OSR community it's known as "Shields shall be splintered" and it's a common house rule to make shields a one shot negation of an attack. Then again, the shield also usually offers a passive bonus as well but I didn't want to ramp up the armor too much. I might give it 1 def and 3 uses but with the option to shatter to completely negate an attack.
Ok, so I just tested my alternate armor with some practice rolls and I think I get why the armor value of 1 was chosen. Even two points of armor drastically reduces the amount of damage a character takes because of how small all the numbers are. If a mouse can equip three pieces of armor and gain 3 def it makes a huge difference. They start being able to shrug off attack after attack without taking any damage at all. I might play around with it a bit more to see if I can settle on something that allows for shields to be a separate item without breaking the game, but I don't think I'm going to have them grant a point of defense or be able to negate three attacks. But at the same time, I don't want the player to not have something they have to give up when using the shields shall be splintered rule either. It should cost something to sacrifice your shield. So basically I'm not really happy with either solution at this point.
Usually any time my group impliments some kind of numerical damage reduction we also use a minimum damage rule. basically just have the ability to tank up be there, but attacks will always do at least one damage.
So what I've decided is that the shield and Helm roll their usage die immediately and prevent damage and take a usage only on a 4+. So if you are wearing all three and you take 5 points of damage you roll a die for your shield and a die for your helm. Lets say you get a 5 for the shield and a 2 for the helm. Your shield takes one point of usage and you take 3 damaged (5 - 1 armour - 1 shield). The armor only takes usage damage at the end of combat, and as before you can sacrifice your shield at any time after finding out the result of an attack to cancel it entirely.