Attempts to carve out local spheres of influence will cause complications, but for the immediate future, the struggle to force Afghanistan into one camp or another, will likely not be successful for either side. Besides, it is important to keep Iran in mind where Afghanistan is concerned. If they decide to help India, like they are doing with Chahbaar, then Pakistan will find it quite difficult to hold on.
This idea of leaving Afghanistan to the "tender mercies" of Pakistan is simply absurd. And as you rightly aver, all efforts to carve out "spheres of influence" are only fraught with hazards for the world at large. The Age of Imperialist and Colonial thinking is over. Even a half-baked
Banana Republik in Africa will be more assertive than ever before in History.
Now as far as Iran is concerned the havoc being created in the name of Sunni Revivalism in the ME is simply going to get the backs of the Ayatollahs up like never before. So do you think that they will countenance any expansionist moves by Pakistan in Afghanistan?
Another stark reality is that Pakistan is nowhere near possessing the clout (Military or Economic) that it did at the time of the last upheaval in Afghanistan after the melt-down of the SU and the exit of USA from Afghan which led to the Taliban take-over.
Now Pakistan is faced with a neo-Taliban which cannot be fitted into the familiar (and oh so comforting
)matrix of Good Taliban/Bad Taliban. The inter-mutations that are taking between these Taliban factions that exist today are becoming unfathomable even to the "old Afghan hands in the Pakistani Deep State".
The emerging scenario in Iraq, is ironically a god-send to Iran; where primarily USA as well as other countries will now scramble to mend fences with Iran. Which will be another setback to any Pakistani moves to re-gain ascendency in Afghan matters.
There is probably only one rational way out for Pakistan to handle Afghanistan in the future; i.e. give up all ideas of turning Afghanistan again into its exclusive back-yard or lackey and instead try to create a more equitable relationship with Afghanistan while working in sustained fashion to bring stability there.
Chah Bahar is a reality and one that will increasingly be a lynch-pin of the Iranian effort to regain stature as a regional power. The fact that India has interests in Chah Bahar too will be used by Iran to the fullest, make no mistake about that.
The ideas of the
"Dull Dulles Brothers" just cannot be re-incarnated now, even the minor players are less Lilliputian now than the hoary days of the Cold War.