Well, three new WIP nations and a thing about plate armour.
Everyone seems to love plate armour, but have you considered the downsides?:
 - Low manuverability
- troops get exhausted quicker
- weak to bludgeoning weapons
- Restricted swimming, bow use and evasion
- higher vulnerability to disarming, sword-breaking and blinding
- weighs down calvalry and transport, meaning it takes longer to move a legion from one part of the country to the other.
-Snags in forest enviroments, making you even more likely to be hit

Plate armour is for damage-soaking juggernauts who kamikaze into the battlefield and pray their armour is tough enough. And while it is doubtlessly the best protection against swords and spears, it is highly suspectable to warhammers and clubs, which cave in the plating and make it even more awkward to move in. Also, repair costs will be insane. Now let's think about a light armour like leather:
-Lightweight, allowing for faster movement
-Not awkward to move in
-Vulnerable to slashes from swords
-Doesn't slow down cavalry
-Only slightly hampers swimming speed and forest movement
-easy to transport
-fairly cheap to buy and maintain
-Doesn't provide a great deal of protection, so soldiers will rely on agility rather than armours

Obviously, leather is a light and cheap resource, but a soldier can only take one or two hits before he's incapacitated, and you can forget about taking a tower shield with you. It'll just get rid of your agility.

Chainmail and scale armours are a happy medium, but are suspectable to piercing hits (Lunges, spears, polearms). They can take more punishment than light armour, but not as much as plate. They are lighter than steel, but heavier than leathers.

Add a bit of variety into the troops. Light armour isn't worse, just different.