Giving Galicia-Lodomeria to Hungary and splitting Croatia off would probably be the best thing to do. It would also be a nice reward to the Croats who stayed loyal to the Habsburgs in the Revolutions. The stumbling block there would of course be the Hungarians, but Galicia-Lodomeria may placate them.
And nay to giving South Tyrol and Trent to an Italian State, its very German, and has been historically part of Austria for hundreds of years. Italian Nationalists be damned.
Istria or Dalmatia, then, as they were acquired from the Venetian Republic.
Trent was ethically Italian in the lower parts, so the claim is not utterly ludicrous. The fact that they were part of Austria since the 1500s IIRC would be a bigger stumbling block. Then again so was Austria. IMHO Ferdinand might get one of the three if he pushed for it- Trieste/the Littoral would be more likely to stay due to it being Austria's only port on the Adriatic, Dalmatia would more likely go to Illyria/Super-Croatia, the Trentino would be carving land from Austria proper as opposed to a successor kingdom... I think a proposal such as entertained by A-H pre World War One- part of Trentino with a border favoring A-H and the Friuli up to the Izonzo- would be the most he/ Lombardy-Venetia could get barring a major uprising or calamity or war.