No matter, what you are thinking about the addition of the US (pls not under this Thread), i like the Age Up Mechanics. They seem very fitting for a federal state… like germany. In fact there have been some threads with the exact same idea for Italy and Germany before. I think it would greatly benefit the flavor of Germany as a civ and also please all prussia and austria-hungary fanboys so here is my proposal:
Age2:
-Hanseatic League/ Hamburg,
some bonus with shipments or xp trickle
-Bohemia,
maybe war wagons an age earlier (?) ~i know, that the population in bohemia was mostly czech
-Würzburg,
Counter-Reformation the church unique tech (mostly catholic techs); or some bonus for architecture
-Thuringia,
center of reformation gives new/different church unique tech
Age3:
-Swabia,
enables all german mercenaries at european saloon/ other merc. bonus
-Bavaria,
replaces germantown farmers; something something beer
-Saxony,
something with Meissen porcelain or a buff for Uhlans, since they once where kings of poland
-Hannover,
something related to Great Britain, since their Prince inherited the english crown and became George I.
Age4:
-Frankfurt,
some coin/trade related bonus; or some bonus, since it is the birthplace of the german constitution
-Schleswig-Holstein/ Kiel,
some bonus for warships or like the NewJersey Canal card
-Rhineland,
some eco bonus since it was germanys most industrial region
-Prussia,
enables Landwehr/Musks and Grenandiers
Age5:
-Austria-Hungary,
enables Magyar Hussars and Pandur (?) /Grenadiers
-German Empire,
sends two heavy cannons (/Krupp Guns)
-Großdeutsche Lösung - ?
As you can see, most ideas are just “reskins” of existing age up bonuses or cards from the homecity. Ofc they are not ballanced and you need something like 200wood etc. aswell. I wouldnt copy the US system 100%, since germany already has a problem with getting all their shipments, so i would preffere to give them some of their card bonuses as an age up (e.g. Bavaria → German town farmers). This wouldnt be OP, since they wont recive uhlans for it.