I think generally there are some really good looking units, there are historical inspirations or they do look authentic enough that it is believable or it is possible to look past and one of those is the feudal age men at arms for the HRE.
I will use the English as a comparison, as that allows me to put an approximate time frame. The Early MAA for English seems based on armors around 1000-1100s. The HRE however has an almost 14th - 15th century style with the visorless sallet and plate armor, the Castle age counter part is around the same.
I did a concept in 3D of how a different HRE MAA could look. It would also be possible to give him a more teutonic knight look.
Normal colors
Age of Empires IV-ified.
Still not 100% in the same time as the English, but closer and allows for a bit more believable or closer approach if we play it by a long approximate. He will still look armored as the original does, ofc he would have the shield and the upgrades as well.
Also I would also propose a change to the English line as following visualized by the screenshot below:
Age 1: Round shield instead of the Heater shield.
Age 2: Kite shield, more in line with soldiers from the Battle of Hastings.
Age 3: No change.
Age 4: A two handed sword.
Bonus: Wynguard Footman could get a ‘Pollaxe’ Knightly Pollaxe – Arms & Armor. While removing the kite shield and the dane axe. As both of these weapons would be obsolete, in the “Imperial Age” or late medieval period for England. He should also get a unique model, instead of the MAA Castle Age model. As they are too similar and frankly it looks lazy.
Almost forgot, for the readability concerns, it is quite similar to AoE2 milita-line which is arguably quite readable. It would also be more easy to tell the different upgrades apart, I think it would serve the readability further rather than make it more difficult. More distinct silhuette for each.
That is it for my feedback and thoughts.