I would also like to add that we really need some sort of heavy armor choice early game. It's pointless to have different armor types with different weaknesses if it takes half a game to unlock the second type of armor.
This. There should always be choices involved, you have 5 types of upgrading weapons but only 1 armor tree, a tree of dubious value as it comes with two penalty systems, one of which is set and greatly increased costs. Heavy armor souldn't be a single exclusively late game thing, light and heavy armor should be something you refine over the course of the game, like current weapons.
I am in total agreement with this.
Light armor: Leather (Armor) -> Lamellar (Advanced Armor) -> Brigandine (Masterwork Armor)
Heavy Armor: Chain (Armor) -> Scale (Advanced Armor) -> Platemail (Masterwork Armor)
If you differentiate Light armors and Heavy armors by focusing on the encumberance of each (modifying initiative), and the production/materials input of each, and have the Light armor be roughly 50-60% the defensive value of the heavy armor I think that we would see both styles be useful in general and actually excel in particular situations. Additional bonus in that there would still be light armors useful against late game weapons.
PLUS, then you can give champions Level Up feats which give them bonuses to armor types! Yay choices!