Prussian Luxembourg, French Saarland?

During the Luxembourg Crisis of 1867 OTL, the Austrians proposed that France get Luxembourg and proceed to give it to Belgium in exchange for Belgian territory.

What if something similar had been proposed: France will give Luxembourg to Prussia (or allow Luxembourg to join the North German Federation) and France will regain the portion of Saarland that it had lost at Vienna following the Hundred Days?
 
That it gets shot down? It'd never be acceptable to the German National Movement, and a net loss for the Prussiano policy makers.
 
On top of that, Saarland is much more valuable than Luxembourg from a pure economic viewpoint. Furthermore, giving away Saarland would create a French salient in German territory, which is strategically threatening and undesirable.
 
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