Do you really believe Germany had no area which wanted to be independent in 1815? The king of Prussia declined the crown of 'Germany' in 1848.
Beyond some high blown rhetoric in the afterglow of victory were any practical measures put forward to create a German nation in 1815?
You seem to miss the entire point of both the Metternichian Vienna system and the German revolution in 1848. The latter was was a democratic, nationalist, pan-germanist movement against the undemocratic, particularist princes. So, citing the opinion of the Monarchs is in this case not a good argument. That movement had already existed befor,e it just exploded in 1848. To be exact, the entire point of Vienna was to create a sytsem to keep the the nationalist-democratic movement (which among other things of coruse wanted an united Germany) DOWN.
And apart from that, 1850 he did attempt to unify Germany in the German Union (also called Erfurt Union in the history books as the diplomatic negotations took place in Erfurt). The point was that 1848 was a revvolution by the people, and accepting the crown wouldve meant accepting democracy. Erfurt was about Prussia (who had smashed down the revolutione verywhere, and hence the other states [read:Monarchs] looked to it as protector) uniting Germany in a non-democratic state.
So not only do your examples completly miss the point by a 180°, one even is flat out wrong

Really, there was no part of Germany with an own national sentiment. At most there was loyality to the ruling house and disdain for the democratic compnent in the democratic-nationalist movement, but no own national sentiments. Hence the situation would be directly comparable.
In France, you could as well have a state with the entirety of the population disgrunted, and the state surviving on a loyal army, police and administrtaion apparatus (a small group of people by comparision, that is) supressing any dissent. That was the way it worked in Germany - you could even say that was what the German Confederation was about. It never faced an external enemy, so the mutual protetcion pact parts proved to be unencessary. But it was all about coordination of the supression of the nationalist-democraztic movement (and you can bet those two factors would combine in France, too).
Now, if some of those states carved out of formerly french territory become part of the German Confederation (Alsace, Franche Comte, Lorraine [which ahd only been French sicne 1766 anyways), they would be within the same coordination - and even to states outside that the same mechanism could be applied.
If you believe Prussia, Austria and Russia will remain united and in a position to intervene against France at the drop of a hat then I suppose your right. I don't imagine they will do so. They all have their own priorities and they are not likely to remain fast friends.
IOTL, Prussia, Austria and Russia more or less remained at least informally allied up to the Crimean War. At several points in time, those three conservative Great Powers formed one bloc to the other bloc consisting of the two progressive Great Powers, the UK and France.