This is a very minor quibble, but here goes:
Currently, the blacksmith can craft a Bronze Shield, usable by knights and footmen at level one. It provides two defense.
However, the default knight shield, used to upgrade a footman to knight (their default armor, usable at level zero) provides four defense.
As a result, when knights reach level one they are already using something better than the alternative.
My suggestion: because footmen jump straight into using two handed weapons at level 3, it doesn’t seem like they need, or get a chance to use, the iron shield that’s currently craftable. I would prefer to see the current Iron Shield usable by the knights at level 1-2 and provide 5 defense. Then, it fits between the base shield, at 4, and the best shield (steel/gold-plated or whatever) at 6. That way, the footmen have an upgrade from the wooden shield (to Bronze), and the knights have their own upgrade (from base) to iron.