Quite.
This was the age of nationalism, and any talk of unification was about Austria's German lands joining Germany, specifically the old Holy Roman Empire lands which included Bohemia and Slovenia... but that is all.
What HOI4 and A-H fanboys/girls don't seem to realise is that the fall of the Hapsburg empire was see as a liberation by EVERYONE outside of Austria (Even the Hungarians, who got the sweetest possible deal under the circumstances). By the 19th Century countries were realising the powerful force of nationalism, and the destabilising effects f having lots of nationalities under one border. Yugoslavia was already tearing itself apart y the 1930's, Czechoslovakia, Poland, and Romania were also dealing with varying instability. Arguably, the only remaining successful strife-free multi-ethnic nations in Europe are Switzerland and Belgium (and of the two the latter has often come close
to being carved up again).
A peaceful Anchluss should only be possible with Austria, Memelland
, and the Sudetenland as historically, and perhaps with Eupen-Malmedy, Nordslowenien and Danzig (the city, not the HOI4 prvince) under particular circumstances.
But all the way to the Panonian plains and the Carpathian mountains? That's just silly