My observation is that in many ways nationalism amped up post-Great War, the war seeming to reiterate the primacy of nation, nationalism and that separation which gives us an even deeper notion of cultural or ethnic competition, superiority, inferiority and the Darwinist struggle to the death. Imploding A-H for me is fueling the violent cycle of nationalism rather than expressing ideals of independence. Obviously we have linguistic, cultural and ethnic oppression, minorities do not feel powerful enough to get opportunity, respected enough to get value out of being part rather than apart. And for me "German" is a language, within the A-H I think it can be a unifying element, as a lingua franca it binds the diverse peoples, to be "German" is to speak the language, and in any scenario I think Germany is the dominant player, not unlike OTL, its economy is the focus of Europe, thus A-H can consolidate Europe upon its core economy, giving access and leveraging these diverse "states" more than they got by being shards of the broken Europe. So I acknowledge that "German" is still going to be a dominant if not domineering force. But how did English or French or Russian do?
So a surviving A-H is going to have to do better to survive, it must address the problems rather than quit and devolve into what we note negatively as "Balkanization." I do not believe FF was on a path to do better, he merely wanted to double down on "German" dominance, but I think Karl had a better grasp of the issues, if so then he is opening up the Empire to its parts. But that too is fraught with danger, once giving a say, next is autonomy and quickly it can become independence. So what A-H needs is both value in the combination as well as risk in the breaking apart.
First I do not believe the Kaiserreich wants Austria and next I do not believe the Hungarians want to merely break away. Those are the extremes not the default end for A-H. The Poles want independence but could be included. The Czechs are about the same. I do not believe the Croats or Slovenes wanted to be jettisoned or added to Serbia. The Galicians are only leaving if an independent Ukraine is forming. Post-Great War there is still a lot of gravity to the Empire but again it needs more to survive longer term.
My opinion is that it moves to something similar to Germany, a more federal framework, that is the nearest working model, it has local recognition, regional (ethnic or linguistic) representation at one level and overall representation if a national assembly is placed into the mix. The two legislatures contributed to the divide, I think Vienna and Budapest need to be reduced to merely Landtag status, and I do not know if that is in the cards. A Bundesrat could bleed off the ethnic, regional and linguistic pressures that pull the peoples apart enough to let the national assembly be a better mixing of interests to cross-cut those pressures. If we get that then I think A-H begins to show that despite differences a functioning state with many languages, multiple cultures and even antagonisms can still be, the legacy would be a less divisive model, less emphasis on the purely national, the purely local, the path outward might be better transnational governance, rather than just a state by state the systems recognize that you indeed need the melting pot where differences debated are more than language, culture or ethnicity differences. Longest term it could be a paradigm shift for Europe and the world. As always there is plenty for TTL to grumble over and it might look rather unfortunate to have not created so many "independent" states yet I think A-H stands for interdependence, something that if successful can build a better ATL, a world becoming united in diversity, unafraid of the connections, the inclusion.