What is the smallest plausible Germany that can legitimately call itself a unified, complete Germany? Largest?
Theoretically, you could exacerbate the bigger state rivalries throughout the Enlightenment to the point where "German" makes as much sense to a Saxon as "Scandinavian" means to a Finn. Sure, we might be part of that area, but that's not who we are.
I'd say the smallest Germany is modern Germany but with Schleswig to Denmark, the Saarland to France, and an independent Rhenish Republic - but it might be hard to get those lands taken out in the West and also have Germany lose all the lands east of the Oder-Neisse line in the East.