I just did this way, from Shiraz until Islamabad in 6 days (in my small car, it was pretty tiring but i did it).
No particular problem.
Sometimes the police escorts you, sometines not. When they escort, ask them to go behind, it is much better for the view and for the speed. (they either go very fast or very slow otherwise).
I don t know the way you planned but leaving Quetta I advise a lot the road going to Loralai via Ziarat (if you spend night in Ziarat, spend night in Shalimar hotel for 200 Rupees, the boss is really nice).
Hey Tom, how are you doing since Jordan ? Where we met with that swedish, christmas trees selling bicyclist ?