A "German Unification Wars Mod" would be awesome. Covering the three wars that led to the final unification of Germany:
The Second Schleswig War (1864)
Prussia & Austria vs Denmark
The Austro-Prussian War (1866)
Prussia vs Austria (both supported by their minor German allies)
The Franco-Prussian War (1870-1871)
Prussia (and minor allies) vs France
Besides finding a modding team that could make this, there will be a huge task ahead for those making such a mod when it comes to balancing. The Prussian Dreyse-gun (needle gun) as well as the French Chassepot rifle are both about four times as fast to fire as the minié-rifles that the Danish and Austrian armies were equipped with at the time. And even though the Danish and Austrian rifles were a bit more accurate, it doesn't make up for the superior firepower of the Prussian and French rifles. Ofc one could then chose simply to make a mod for the Franco-Prussian war, where the infantry weapons were closely matched, but I think it would quickly get a bit boring with just two teams. But that might just be me.