Spheres of influence, nothing else...
I've heard elsewhere in the site that Austria-Hungarian leadership had abandoned all territorial ambitions before the war due to practical reasons, But I can't be sure if that's true...
In any case, both the Germanic and Magyar populations are gonna oppose the annexation of majoritarily slavic lands, even if the Parliament was closed since 1913, they just weren't going to allow the entrance of more trouble-making, freedom-loving slavs...not the proto-nazi pangermanics of Vienna, not the agrarian aristocratic oligarchy of Hungary, not the traditionalists of either side...
So, Economic and political sphere of influence over the Balkans, perhaps a Habsburg King in Poland...that's the typical...annexation of Montenegro? anything else is likely to led to civil war and collapse...