I still like my idea of a Pyrrhic victory for Serbia—it gains land that does nothing good for it, prone to Bulgarian-funded rebels like what happened in Macedonia IOTL, while also making major concessions to Austria.
Meanwhile, Bulgaria falls firmly into Russian orbit, especially if the Ottomans invade and take back Rumelia as well. This is great news for Russia—they are closer than ever to the Straits with a Bulgarian semi-vassal.
What does this mean for everyone else? If Russia’s backing Bulgaria more then Britain probably moves to support the Ottomans, which could have butterflies all the way to the Great War!