How about Hungary? Remember than the Croats, Slovenes, Bosniaks Czechs, and Galicians of all colours had nothing in particular against the Hapbsburgs. If anything is going to end A-H, it will be a breakdown of the dual monarchy system.
Serbia and Romania were not part of the Hapsburg realm, only members of the same ethnic groups. Why will the nationalists prevail? Any particular reason?
Why not?
GAAAAAAAAH!!!
Yes, of course we'll just kick out the ancient Sultan and Commander of the Faithful, ruler of an Ottoman realm which is springing back from the Balkan wars and, with the discovery of oil reserves in its southern provinces, is probably booming, over nebulous "economic mismanagement". And then we'll have this make Turkey completely unable to defend their own capital and see off the notoriously efficient, well-equipped, and motivated Russian army. Oh, and Britain just stopped caring about the balance of power in the Balkans and ME, apparently.
GAAAAAAAH!!!
Okay, seriously, why is Europe suddenly fated to turn red, except of course Russia. Also, for a given value of take, Social Democrats had already taken over Germany.
Anti-what-nows? I don't think anybody was keen on Tsarist absolutism, except maybe the Tsar and his family.
Okay, having finished GAAAHing, my own thoughts. Presumably the premise is "WW1 as we know it, Germany decides not to risk it all". Borderline ASB, but yeah. All else being the same, we end up with Austria accepting Serbia's deal on the ultimatum and things staying fairly stable. There are plenty of other catastrophes waiting to happen, but with Germany becoming strangely pacfist, a great many can be defused. If I go further I'll have to get into genuine ASB territory.
The A-H empire won't go on any further than the 30's because of the rise of liberilisum and nationalisum. Nationlist uprising and guerilla wars have to be put down by the army, big problem as that is in desperate need of re-form; the only thing holding it together in peace is the kadets, let alone when you have uprisings left right and center.
Britain will intervene in Turkey for exactly that reason! to stop Russian influence, perhaps see the Russians gain Western armenia etc, Britains make gains in palistine etc and Sultan replaced with republic.
There were plenty of people who supported the Tsar (pre WW1) especialy in the military and the Church.
Yeah your probably right about the socialists etc, they were only so prominent during the post WW1 depression years (defeats the idea of the scenario as there was no war)