The Austrians had an empire in 1918. They didn't have one in 1919. That's losing it in my book and I don't see a big difference. The allies did not demand the dismantlement of the Austrian empire. The allies forced tha Austrians to demobilise their army. The Austrians could have used it to stop their empire from falling apart. The end result was the same.
True. the Russian empire did not fully collapse but it lost plenty of territory after WW1. Poland, the Baltics, Finland. All nations that managed to become independent because the Russian were too weak to keep control. And yes, they came back with a vengeance later on.
All I'm saying is that multiethnic empires should face a much more real internal minority problem. If they're weak then small or big pieces should break off or the whole thing should be able to collapse. Accepting a forced disarmament, losing a war or having a high WE should trigger (massive) national revolts for non accepted cultures, especially if the imperial government is repressive. If it's liberal the non accepted minorties will probably demand independence too but they might do it peacefully first.