That's an awesome analysis and some good proposals.
However, I cannot totally agree with the enthusiasm to make armor so much better. The reason is that the game lacks almost any negatives which come along with armor. Making armor too good leads to big imbalance therefore.
You know the story of the death of the Earl of Shrewsbury in 1098? When the fleet of Magnus Barefoot (or Bareleg, as others call him) was near his lands, the earl rode to the shore with his force, and two archers from the ships shot at him, one arrow hit the nasal of the helmet and deflected, the other hit through the eye and killed the heavily armored knight immediately. Such total failure of armor was not extremely seldom, because most armor had gaps.
So we needed a percentage for when armor was applied and for when it was of no use at all (like in Kenshi). If we had closed helmets we needed, for example, negatives to Athletics (cause breathing is strongly affected by closed helmets), perhaps restricted vision. We needed exhaustion from the weight and heat (or cold) coupled with the wearing of armor. We have nothing of this, no negatives (except weight on foot), armor protects all the time, so it must not protect as much as it would in reality if hit.