I'm not so sure whether there was a significant Turkic presence in Central Asia in the second or first century BC. The major nomadic threats were Iranian tribes like the Saka or the Parni.
I don't think an Argead Empire would really be that large.
Update.
Epilogue
Little, but very interesting TL. However i hoped to see the post-Imperial history one day...
There were the Yuezhi though I wasn't completely sure whether they can be classified as Turkic. Nonetheless, any Han movement westward would force them to move.