Yugoslavia happened post WW1, not 2. In any case the ex Austro-Hungarian areas of the SHS state and the Kingdom of Serbian didn't have anything to do with each other since the late Roman Prefecture of Illyricum.
Yip, nobody says it would be perfect. Historically it's not so easy to say how the country between Persia and India was organised, especially taking into account the "natural" border of Greater Persia might be considered on the Indus, as well as India's "natural" border along today's Pakistan's border in Baluchistan (continuing towards Herat), and how long that area of modern-day Afghanistan was ruled by Mongols or Turko-Mongols.
But one thing is for sure: A lot of problems today stem from the division of the Pashtuns.
With Russia's weakness keeping it from plotting another "Great Game", a more-or-less stable (of course not internally!) Pakistan, and with the SIS running most of Afghanistan anyway, the chances might be good. And the alternative from a Pashtun view would be unacceptable for Pakistan.
Just think that such a Durranistan would pretty much cover that "middle ground" between Persia and India (leaving out the classical Baktria north of the Oxus) and would have some pre-colonial justification, which might be actually accepted by the people.
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