I have been wondering about this for some time.
How are you going to represent the ethnic diversity of lets say the Austria-Hungary? There were regiments that we recruited specifically in then Slovene lands. Sure the officers were for the most part Austrians, yet the fighting spirit of each unit was also linked to where it came from and where it fought. Also let us not forget the ferocity of certain troops that instilled chills in the defending army.
So, will there be a recruitment pool with limited number of regiments one can draw from them, or will there be just recruitment en masse for each country?