Well desperate attempts can lead to anything as history thought us coughRusso-Turkish alliance vs Egypt cough...
Well, don't forget Russo-Turkish alliance against French Republic which resulted in creation of a
republic sponsored both by the Russian and Ottoman empires (Septinsular Republic), which sounds as an oxymoron.
Jokes aside, Greater Bulgaria within Russian influence, the Serbia coup of 1903... after 1903 Austria-Hungary would be paranoid as all their neighbours except Switzerland are hostile. Considering a Russo-German alliance is there as well.
Well, if A-H is a member of
Dreikaiserbund then it surely should not be afraid of Serbia and Bulgaria (I'd dare to say that a chance of the Serbian troops marching along Kärntner Strasse had been quite low, anyway
). The only remaining enemy worthy of a serious consideration would be Italy and if A-H is not involved into any other war, it would probably be able to hold its ground.
As for the general notion of the "interests on the Balkans", I honestly can't consider it as just a popular type of a paranoia. None of the Great Powers competing in the region had any serious economic interests there (as I understand, serious mining was not going on in the late XIX - early XX) and as far as the strategic interests had been involved, they were mostly dead after the Ottoman Empire ceased to be Europe's scarecrow. Sphere of influence makes practical sense if you can get something out of it, not if you have to take care of it.