Another answer for Talos is that, when the borders are redrawn, inevitably you'll have irredentist tendencies in the region. Slovenia with Croatia, Hungary and Serbia, Romania and Hungary, Macedonia and Greece, Albania and well, everyone, Turkey and Greece, Macedonia and Bulgaria, Bosnia and everyone, Macedonia and Kosovo.

Some of these countries are fighting over long established borders. Some over borders not yet drawn through agreements, and the irony of course is that, inside the EU, these borders matter much much less than they do outside.

I argue this with people about the Cyprus situation. Beyond a certain threshold, the Cypriot Republic will not negotiate its rights in the north away, no matter what. If Northern Cyprus becomes a recognized state, and then enters the EU, then in many, many ways, the citizens of the south will have MORE RIGHTS in the north than they would have under a UN plan that contained so many EU derogations that took their rights away.

This is why creating borders now, as you wait to enter the EU, seems a bit silly. Administrative borders are best, not national borders, since none of these countries have a standing army, and they all need international money to stay afloat.