To be honest, I think simply drawing steight lines would have caused similar problems between ethnic groups. As it is the boarders were mostly drawn on historical boarders, not taking into account that the villages especially in the boarder regions what was Austria-Hungary were very mixed.
As I am Austrian myself I will try to go over those boarder possibilities, but don't hold me to it. I ain't no expert.
South Tirol staying with Austria would be a possible alternative, if the Italians would back down on their claim. That region was unified a long time and sentiments of even the local italian speaking minority were to stay as a unified Tyrol. A few people from the area told me that there were serious talks about reuniting with Austria up into the 80's.
Yet those areas would prove among the easiest to devide among ethnic boarders. That one would run somewhere south of Bozen and north of Trento.
Carinthia could have lost or gained more land. If memory serves right there were referendums about the Gailtal area. Could have been after WWII as well though. To be honest it would have made more sense if Carinthia would have lost more territory to Slovenia (Or better the Kingdom of Croats and Serbes or however it was named) than it did.
Styria was seriously cheated on territory. Austrian mainorities down to Marburg/Maribor as well as quite a few kilometeres into Hungarian territory. The problem, especially with the Hungarian territories was that those were historical part of Hungary and not Austria. Same is true for the area around Lake Neusiedl, Pressburg here to name a well known example (42% German, 40% Hungarian, rest others mostly Slowaks).
The boarders on the north to Czechoslovakia were a lot in favour of the new state and gave a lot of German dominated territories away. I'm not talking about Silesia or North-Bohmia there, but the areas on the fring of the new Austrian state.
Of course there was no way in hell that Austria would keep the German dominated areas in the Gottschee, Transylvania or around the Danube in the Hungarian core lands, or any other of the encaves for the matter.
As it is the only really likely areas to go to Austria would be the area around Lake Neusiedl, depending on Hungary, and the South Tyrol, depeding on Italy. The areas in the north were quite happy with garantees of autonomy within the new Czechoslovakia (what didn't quite work out later on) and as said the ability to claim enclaves is very unlikely.
Don't know really much about the other countries to talk about those.