I think there was no real need to 'satisfy' the territorial claims of newly created states like Czechoslovakia or Yugoslavia. Czechoslovakia could have worked anyway without the southern Sudetes or the southern Magyar districts of Slovakia, and the same for Yugoslavia regarding Lower Styria and most of Vojvodina. Italy could have received more parts of Dalmatia rather than the South Tyrol.
The Allies accepted Czechoslovakia's argument that Bohemia's historical frontiers must be respected for strategic and economic reasons. Wilson referred to the Sudetenland "which is undoubtedly predominantly German in population but which lies within the undoubted historic boundaries of Bohemia and constitutes an integral part of her industrial life. In such circumstances ethnographic lines cannot be drawn without the greatest injustice and injury."
https://books.google.com/books?id=L7UOyPGYBkwC&pg=PA191 F
One thing to remember abooutthe Sudetenland is that despite the treaty banning an Austrian-German Anschluss without the consent of the League Council, everyone knew that in the long run such a union might come about. So giving more Sudeten territory to Austria might in the end amount to the same thing as giving more territory to Germany which would then surround Czechoslovakia on three sides and could easily crush her--as indeed would happen twenty years later.
In the same way, letting Austria keep South Tyrol might ultimately mean a larger Germany extending south of the Brenner Pass and potentially menacing Italy. In any event, Great Britian and France, having induced Italy to joiin the war effort with the Treaty of London promising Italy the South Tyrol, felt that they could not go back on their promise. True, the treaty had also promised Italy much of Dalmatia, but if one had to choose between limiting self-determination for the South Slavs versus limitig it for the German-Austrians --well, the Allies' view (whether or not historically sound) was that the latter were responsible for the war and should get less consideration.
As foe Vojvodina. even the 1910 Hungarian census--which was certainly not biased
against Magyars!-- showed that they were only 28.1 percent of the population compared to 33.8% Serbs.
https://en.wikipedia.org/wiki/Demographic_history_of_Vojvodina#1910_census Even for the city of Novi Sad there was at most a narrow Magyar plurality: "According to the 1910 census, the city had 33,590 inhabitants, of which 13,343 (39.72%) most frequently spoke
Hungarian language, 11,594 (34.52%)
Serbian language, 5,918 (17.62%)
German language, 1,453 (4.33%)
Slovak language, etc. It is not certain whether Hungarians or Serbs were largest ethnic group in the city in this time, since 1910 census is considered partially inaccurate by most historians because this census did not recorded the population by ethnic origin or mother tongue, but by the "most frequently spoken language", thus the census results overstated the number of Hungarian speakers, since this was official language at the time and many non-Hungarian native speakers stated that they most frequently speak Hungarian language in everyday communication. The city was also home to 2,326 Jews, of whom many were native Hungarian speakers. Another aspect of the census was that it not only recorded permanent residents of the city, but also temporary residents, who did not live in the city, but were situated there as part of the civil and military services.
[7]"
https://en.wikipedia.org/wiki/History_of_Novi_Sad
So fae as the Allies were concerned, I think they would tend to dismiss any complaints from German-Austrians or Magyars by saying "Well, really you should have thought of that before presenting Serbia with that ultimatum in 1914..." (Again, I'm not necessarily justifying that view of the origins of the Great War, only saying that it was the one held by the victors.)
