Yep, it would be an extremely gigantic butterfly net lol. No doubt about that at all!
I think that Serbia will insist on acquiring the Slovenians and Croats for itself for its Yugoslav project, and I don't know if the victorious Allies would actually be willing to oppose the Serbs in regards to this. Honestly, the more that I think about it, the more that I think that your three states idea would be realistic. Having Silesia go to Germany would probably be unrealistic since I'm not sure if the Silesians themselves would actually want this and, in any case, this would seem to reward Germany after it lost a World War, which would likely be viewed as unacceptable, similar to why the Allies blocked an Austro-German union in 1919 even though the Austrians themselves genuinely wanted such a union. So, we could actually see a similar post-WWI map in this TL to the one in our TL, just with an independent Silesia added to the mix. I think that giving Silesia to Czechoslovakia might be difficult because it might then create an excessively large German minority in Czechoslovakia, which I'm not sure that the Czechoslovaks and/or Allies would actually want. The Sudetenland was trouble enough for Czechoslovakia, though at least it had defensive value and was a part of the historical Kingdom of Bohemia.
In this TL, in the 1930s, I wonder if whatever equivalent of Nazi Germany there might be (if there actually is one, of course, which is certainly not guaranteed) will go for Silesia first and only later for Austria. Would the Anglo-French actually be more willing to fight for Silesia than they were for Austria? Frankly, I doubt it. Though this would likely mean that Silesia's independence gets restored if WWII goes the same way for Germany, if this extremely massive butterfly net would still be in effect by then lol.