I can see a much more modest German expansionism program developing under a Ruprecht administration. Anschluss and regaining Danzig are obvious, as is lifting of the military restrictions in exchange for whatever replacement penalty the French and British will want for it (reduction in reparation reductions?). All the German areas of Czechoslovakia would take political capital better spent elsewhere, but I can see the Egerland and maybe the German parts of southern Czechia being pried loose.
As for OP's concept of a German-backed Habsburg restoration in Hungary? That would probably come later, though it'd be on the agenda. More important for Hungary and her new ally, regaining the Hungary majority territory lost at Trianon. Northern Transylvania and Székely Land are a longshot, and would be either left for the future or written off entirely.
Regaining South Tyrol (not Trentino too, obviously, just South Tyrol) would require giving Italy something in return. Good solution? Encouraging all the rifts developing in Yugoslavia. Could get all of Yugoslavia's neighbors involved in that one, even Romania would have some majority Romanian areas on the border it could nibble off. Maybe even get Greek support for the project; deal could be made that in the event of a fragmentation of Yugoslavia, Albania's gain of the Albanian portions will be partly balanced out by ceding the majority Greek portions of Northern Epirus.