Nothing is going to pop off in the balkans for some very simple reasons.
1. A lot of powerful people (including politicians) are running rackets and money laundering schemes in that region and they'll make sure those don't get disrupted.
2. Everyone is getting foreign gibs and a war would again disrupt that. No one wants that.
3. Everyone would get their shit pushed in period because everyones armed forces are garbage in the region. Serbia has been "modernizing" with chinashit and russoshit, and i'm sure their modernization efforts or on paar with russian modernization where they give the new stuff to a couple battalions and call it a day. Greece is still using soviet shit they haven't even bothered modernizing but they have conscription so at least they'd have numbers. Romania is a joke. Macedonia is a joke. Albania has attempted multiple modernization efforts that have failed with a few exceptions in small arms. No active armor units, no active jet units, questionable AA capabilities and the inactive equipment they do have has been in storage since like the 00' with no one trained in them probably unless they start pulling 60 year olds out of retirement. Croatia and Bulgaria have had more successful modernization efforts but i'd still consider them sub paar. Kosovo has the kosovo security force which has probably the most modern infantry in the region, but thats it, just infantry.
4. Too many hidden weapon depos and national spirit for any land grab to not result in years long insurgent action or partisans if you want to be nice.
5. Foreign powers would get immediately involved.