Hopefully CA introduces more Han Dynasty era armor into the game. Way too many units in the game (from lower ranked militia to higher ranked elite troops and heroes) are wearing some sort of leather armor, and too many elite units are wearing apron armors that have no protection for the sides.
Leather was expensive (tanning process is long and expensive) and is weaker than cheaper alternatives, so it was very rarely used as armor. Rawhide was much cheaper than leather, and is much tougher/stronger than leather. However, rawhide is very stiff and not flexible at all, so it has to be cut into lamellar plates and/or scales to be used as armor. That's why the Qin Terra Cotta soldiers are wearing lamellar plates - those are stiff plates of rawhide that have been lacqured and painted. Not to mention by the Han Dynasty era before 3K's timeline, metal lamellar would have become common.
It is also strange that so many armor in the game (especially for elite units) seems to be some type of "apron" armor that doesn't protect the sides, when lamellar vests that wrap around the side would have been the most common form of armor. However, you look at the Qin Terra Cotta army or depiction of Han Dynasty troops, the lamellar armor are not aprons, but are actually vests that protect the side. Even the lightest/simplest of lamellar armor vests that don't wrap around to the back still protect the front and sides. There might have been a few aprons introduced in this era, but it is strange that both low level and high level troops are both wearing aprons without side protection.
Examples armor in the game:
Apron armor 1: https://imgur.com/a/rlbE6wx
Apron armor 2: https://imgur.com/a/8egWptz
Mishmash of apron armors and leathers for warlords and units: https://imgur.com/a/AC6Epue
Examples of Han Dynasty armor:
Pt 1: https://imgur.com/a/jOBHXhr
Pt 2: https://imgur.com/a/FnJciZA
Han Dynasty figurines with painted armor of lamellar vests: https://imgur.com/a/8sskphR
Qin Terra Cotta Army lamellar vest armor: