Yeah having a Germany wanting to rule even more with Nationalist flavor is not something desirable.
As noted above, it is not desirable considering how the last two or three times it had disastrous consequences for everyone involved.
No, a newly nationalist Germany as you intend it is a defeat for Europe. They, as a people, have already an attitude that they think they can tell others what to do. I rather deal with a Turkified Germany than them going all Gott Mitt Uns and I say this as a former political and cultural Germanophile. It is going to be a situation like Kissinger's debacle in Cambodia : trying to prevent something bad and what follows is even worse.
Germany has already ruined multiple times Europe in its history, both as single individual polities and as an unified state, so there is no historical precendent to say it will be beneficial to the continent or, for what it matters, the world. It didn't work before, it won't work now just like Communism did that time and time again.
Because you open Pandora's box if we let the genie out of the bottle: all bets are off... And I won't be surprised if we see them asking for Silesia and East Prussia or Alsace back.
So no National Germany. Matter of fact, it would have been better if there had been two, or three and five.