Let's assume that ITTL Russian-supported, Prussian-led unification of Grossdeutchsland and Italian unification occur before than or at same time as Belgian Revolution. Let's also assume that for various reasons the great powers are not willing to come up with nationally-artificial neutral buffer states (like OTL Belgium) or other kooky Metternich-Talleyrand solutions like "free zones" with nationally bizarre borders if they can avoid it at all.
Let's also assume that Alsace and Lorraine (all of it, not just the 1870 part) were carved up as an independent kingdom after Napoleon, another nominal member of the old German Confederation like the duchy of Luxemburg (which at this time includes OTL Belgian Luxemburg, is in personal union with Netherlands, and is garrisoned by Germany too). The fate of independent A-L and Luxemburg after Grossdeutchsland unification is still up in the air, different sectors of their population want to stay independent, join Germany, or join France.
What would be a plausible territorial settlement ?