It’s pretty well established that the “Germans” are basically Austria:
Most of the things you have listed still point to Austria.
Multi-Ethnic Unique Units
In the “Germans” you’ve got Polish, Czech, and German unique units. The only entity that encompassed all of those is the Austrian Empire.
Polish Uhlans would need to come from the Galician or Danzig regions of Austria or Prussia which fall outside of the HRE.
War Wagons were basically out of use by the game’s period and are more just to represent the Czechs who were primarily part of the Austrian dominions.
Settler Wagons are generically southern German, but that region was broadly under Austrian aegis (Prussia formed the North German Confederation for a reason). Some areas are even under direct Austrian control as shown on this map:
Cards and Unique Church Upgrades
The Catholic and Austrian themed church upgrades are exclusionary the majority of German regions that were Protestant.
Wallensteins Contracts - Austrian Reference
Tilly’s Discipline - Austrian Reference
Palatine Settlements - Austria controlled territory in these regions.
Polish Winged Hussars - Reference to Battle of Vienna
Superficial Prussian References
Changing Prussian references to turn “Germany” into Austria would be an issue if it required disruptive changes like changing units or mechanics. Fortunately, removing the Prussian references would have no gameplay impact whatsoever.
House of Hohenzollern - This is a very recent change in name and probably not set in stone
Changing “Needle Gunners” is as simple as altering a few snippets of text.
If Prussia were ever added to split Germany, the leader and home city could just be transferred to them. Creating an Austrian appropriate home city and leader (such as Vienna and Metternich) wouldn’t be more work than any other new home city and leader.