Melee Weapon Damage (3) - Armor for Thieves and Magic Users

Anyone can dress up. Anyone should be able to wear armor.

Thieves

Can't attempt thief skills in metal armor

AC: 1 worse in metal armor - reflecting lack of training

May use a shield only to cower (see below) 

Magic User

Can't cast spells in armor.

AC: 1 worse leather, 2 worse in metal armor - reflecting lack of training

While wearing armor and wishing to use wands or staffs useable by MU only - make save vs spells to use, still uses a charge regardless. Same applies in no armor and trying to cast a spell while restrained in some minor way.

May use a shield only to cower (see below)

COWER behind shield: – can’t attack, -2 AC (2 better AC), +2 saving throws, takes 1 full round to drop shield, no XP for combat

I like this cowering rule. Brave brave Sir Robin doesn't just have to run away any more.