There wouldn't be a whole lot of German players in the new Super League, not enough for a full squad. England and Spain would certainly be hit hard.
Depends on who qualified for this superleague. If Bayern, Dortmund & Leipzig made the cut, while Barca/PSG/Chelsea got in from their leagues; you'd have most of the NT there.
Sane/Werner - Havertz - Gnabry
Goretzka - Gundogan*
Kimmich
Halstenburg - Süle* - Can* - Klostermann
ter Stegen
With a bench consisting of some combination of Werner/Sane, Reus, Brandt*, Dahoud*, Draxler, Kroos, Henrichs, Schulz, Kehrer*, Rudiger*, & Neuer. Plus vets who can still play like Müller, Hummels*, Boateng, etc.; and kids who are breaking through & have NT talent like Moukoko, Samardzic, Stiller, etc.
You could make a good team with the remaining german players, but not one that was as good as this superleague team. Would be left with something like:
Volland
Wirtz - Kruse/Stindl - Hofmann
Kramer - Neuhaus
Gosens - Ginter - Tah/Koch - Baku
Leno
---------------------------
Volland
Wirtz - Kruse/Stindl
Gosens - Neuhaus - Hofmann - Baku
Kramer - Ginter - Tah/Koch
Leno
With Kruse/Stindl, Waldschmidt, Amiri, Demirbay, Geiger/Eggestein, Max, Tah/Koch, Torunarigha, Friedrich. Plus kids who are just breaking through like Berisha, Nmecha, Adeyemi, Jakobs, Thielmann, Leweling, etc.