I think Direct Annexation without Federalization of the remaining non-German parts of the Habsburg Empire would be a bit much but not truly impossible.
That said, if there's anything similar to the French Revolution in such a Timeline, which I find likely, then without any other German States to receive territory most of it will have to go to Austria or an Austrian Client State because they will be the only ones there to get it. Even if you do get German Territory going to some other state this hypothetical Austria is powerful enough they won't be able to stand against them. Either way you wind up with Austria maintaining their hold on the German States without anyone to really stop them.
Especially because if Bavaria is properly integrated that really shifts Austrian Power. This will go a long way to marginalizing the various minorities in the Empire and should help prevent a lot of Austria's instability.
France will be obviously pissed off, but most of the other states will probably be ambivalent about the whole deal. Britain won't mind because this Austria will be a purely Land based Power. Russia is the major wild car in this situation, but they might not mind because with a much stronger Western Direction to their Policy that means Austria may be more forgiving of Russian Power in the Balkans. Alternatively it could mean Austria feels tough enough to outright oppose any Russian power in the Balkans, but that could get Britain on Austria's side.