Lol, that's not an exhaustive characterization of "this generation". Most people are in neither group.
Also, the AfD folks would be rather fighting for Russia, the leftist activists will conscientiously object, and recent immigrants are not allowed to serve. Very weird to mention "second gen immigrants", as if ethnostate-ish racial tension is a wider issue in Germany and they are not normal citizens. I see no difference to children of Turkish migrants serving in the past. Do you realize Germany had mandatory military service before?
> A mix of all will end up obviously in a disaster but selecting on any group will end up in a civil war or coup.
Obviously! Jeez...
Btw. historically, after WWII, one of the reasons to have mandatory military service for every man was specifically to get a diverse army, as a cross-section of society, instead of clusters of certain dispositions, so the Bundeswehr exactly won't become an ideological, political force. Conscientious objection is a legal right for every soldier, at any moment, because of it. The constitution also prevents any sort of "group selection". A homogenized army is much more dangerous to the democratic order, than a diverse one. People thought of this before...