I’d love a fantasy role playing game that incorporates a robust armor system that allows you to mix together different pieces of accurate medieval armor, like gambeson under chainmail or chainmail under a tunic.

There's a weird experimental game called Exanima, which currently just has a dungeon crawler mode and an arena fighter mode, but it does this extremely well. Many many layers of armor and they all affect how you are damaged based on the physics of the weapon and how it is swung.

Downside is that no one moves like a trained fighter, they look like random peasants who are very drunk have been given weapons and armor.

But it's still interesting.