Crown Prince Rudolf has a son instead of a daughter, named Joseph, who has a similar personality and philosophy to Emperor Joseph II. Say he is also born in 1883. How would a hypothetical Crown Prince Joseph get involved in Austrian politics prior and during WWI? Both Franz Ferdinand and Crown Prince Joseph working together may have been enough to topple the old Austrian aristocracy and maybe sabotage the Central Powers, thereby preventing WWI. He would have been young (31 in 1914), but it's possible.
Possibly, Franz Joseph dies in 1913 due to increased stress of having to deal with a liberal heir, thereby Crown Prince Joseph becomes Emperor before 1914. I think he would be pretty critical of Germany and the Central Power Alliance like Crown Prince Rudolf and Franz Ferdinand (a pity that both liberals were killed). Perhaps he still maintains it, but he refuses to go to war if a similar situation to the July Crisis does happen. He probably becomes a Gorbachev in that case and sees Austria-Hungary dissolve under hie rule, at the significant benefit of preventing WWI. Even before coming into power, Crown Prince Joseph can challenge guys like Hortzendorff on Austrian internal and foreign policy too.