As known, the population of Austria-Hungary was made up of 11 major ethnic identities.. When the war ended, A-H broke up as it was instead of forming a new federation of Austria, Hungary with an exclave in Romania, Slovakia, Czechia, Bosnia, Croatia, Slovenia with land ceded to Italy, Sudantenland to Germany, part of Galicia to Poland and another part to Ukraine. Also major part of Transylvania to Romania.
At least Hungary would not feel bitter about the Treaty of Trianon through which Hungary lost lands.
Were there, in fact, any attempts to create such a federation after World War I?
(FWIW, Poland, Lithuania and Ukraine could form another commonwealth on their own (PLU). With an access to the Baltic Sea through Lithuania, the importance of Danzig to this PLU would be diminished. There would be less pretexts for the N-Germany later on to intervene and invade lands outside of Germany.)