I am surprised anyway that there is no “Erzbischof” unit as he would be very German. Those “Erzbischöfe” (plural) had lands and commanded lords and knights. And some religious leaders also went into battle fully armored. Actually when you have a civ like the HRE, you have tons of possibilities for units, techs, mechanics and so on. I really expected more from Relic, because they were so adamant about wanting to be historically rather close to the facts. The HRE in AoE 4 is more fantasy than factual.
This blog gives some insight to medieval Germany:
These are parts of the parade armor of the Erzbischof of Salzburg from around 1600: