Well, if it is to be meaningfully "Afghan", you really have to start with the Durrani: they are generally crdited with _creating_ Afghanistan as a semi-coherent state. Before it was a borderland usually divided between different empires.
The Durrani state was a good bit larger than the current state, at least at the start (see map), and I've seen pictures which show it temporarily in control of the Sind. If the founder has a run of skilled heirs, rather than the losers of OTL, "Afghanistan" could emerge as a sizeable state incorporating much of current Pakistan, eastern Iran and bits of Central Asia as well as Afghanistan proper. They probably end up losing territory to the Russians in central Asia and the British in OTL Pakistan (if they're still expanding, they are unlikely to see the need for a crash modernization program before the British show up and start kicking ass), but given their OTL military prowess they probably end up maintaining their sovereignty.
Of course, the big question is whether they can keep the show on the road: Pushtuns are willing to be ruled by Pushtuns, but they are easy to piss off...and there's a lot of other minorities to worry about.
OTOH, if we have an early 20th century Russian civil war as OTL - well. There's all of Central Asia to pick up...
Bruce