Well, the Big Bad Slobo has been out of business for a couple of years now. Serbia has now reformed, at least by the looks of things in the papers. So why aren't we letting them back in control of their territory? And why especially have we tied the hands of Macedonia? (Hint: The answers to these questions might require getting past certain ethnic labels)
Slobo was decomissioned in 2000, but his legacy has only recently been dismantled, and his legacy in places like Kosovo will require at least a generation to overcome - once the locals figure out that merit based government works better than one based on ethnicity, things will normalize and meaningful Pristina-Belgrade talks will occur.
Allowing Serbian troops back into Kosovo without the acquiescence of the locals is simply a non-starter, however, and while the EU can provide the stick to keep Kosovo a seperate entity in the region, it is up to Belgrade to provide the carrots to bring it back into the fold.
Given what's going on in Montenegro, what do you think the chances of that happening are?
As to Macedonia, the Nationalist politicians lost in their bid to radicalize their populations past the point of reconciliation with another pointless Balkan war. Cry me a river - neither the Macedonian Army nor the ANA were capable of winning a war in Macedonia.