I have been tinkering with the way weapons and armor work in B/X. I think these houserules add some depth to the system without being overwhelming. The armor system below allows for more thematic characters in this system, especially when armor types are abstracted to light, medium, and heavy.
Base AC for all characters starts at 9 and progresses upwards based on Weapons, Armor and Dexterity.
- Small melee weapons add +1 to AC
- Medium melee weapons add +2 to AC
- Large melee weapons add +2 to AC
- Ranged weapons add no bonus to AC
- Shields add a +1 (small) or +2 (medium) bonus to AC*
- Helmets add a +1 to AC (-1 to initiative and ranged attacks?)
- Leather Armor (light) provides a +1 to AC
- Chainmail Armor (medium) provides a +2 to AC
- Plate Armor (heavy) provides a +3 to AC
- Dexterity Bonus**
- Any character can dual-wield and both weapons add towards AC, but only off-handed weapons can be used in the off-hand.***
*Ranged attacks ignore AC modifiers provided by melee weapons but not shields.
**Dexterity bonus is added to AC (Armor + Dexterity cannot exceed +3, anything over is lost). So if a character with a +1 dexterity bonus could wear chainmail for a total AC bonus of +3. If he wore plate he would gain +3 to AC from the plate armor but would lose his dexterity bonus.
***When dual-wielding the number rolled on the attack die determines which weapon has hit. Even numbers are hits from your main weapon, and odd numbers are hits from your off-hand weapon. Roll damage accordingly.