No, it's glued at the core by the prospect that a third round of the previous unpleaseantness need to be averted and the fact that while the degree of influence are variable, in general all members are more or less equal and democracies.
This might be somehow true at its origin, but if the EU still exists today is not because of fear of an eventual WWIII (with NATO would be enough for that).
And 'all members are more or less equal' it's blatantly false...and the democratic quality of some Eastern members is quite debatable. Money rules EU today for good or bad, nothing more, nothing less.
Your Mitteleuropa it's just a German show used as a framework for the sole prosperity of the German nation...as this was the original plan and why the Austrian will want to play the role you give them? They had so much trouble at home and are by now a dependent of Germany, plus before the war and even during they had found extremely difficult do any serious reform.
Seriously, in any Mitteleuropa the Hapburg Empire will count nothing, it's just the first servant of the German Empire, sure with some privilege and the illusion that's an independent power, for old time sake but everyone will know the truth.
You are assuming that Austria would be happy playing the German puppy once the war is finished, but I think that it is likely that they might separate in the medium term, getting back to the 1860s situation.