Yeah, Austria-Hungarian blundervention is the only way Alexander had a chance. I then planned for the Austrians to Install someone else anyway. But who?
If Austria was given the chance to play kingmaker in Serbia at this time, they would install either Theodore Nikolic von Rudna (a Serbian-Hungarian aristocrat with ties to the Obrenovic dynasty) or Prince Mirko of Montenegro.
Both of those choices are kinda bad, in different ways.
This sort of thing (aggressive expansion, or stomping around the region deposing governments) creates new problems for Austria-Hungary without fixing any of the existing key problems. But I guess the changes could still make the Habsburg dynasty blunder its way into longevity and survival.