I think there is some confusion here. The word "A" in Pakistan is for Afghania/Afghan province, mentioned by Ch Rehmat Ali in 1933, when Pakistan was used as an acronym for the first time. But we already named it Khyber-Pukhtunwa. Pushtuns are Afghans are the same ethnic group, infact second largest in Pakistan.
The identity crisis is evident in Afghanistan, where alot of other groups other than Pushtuns live. Pushtuns are only 40-50% of Afghanistan, while rest Tajik, Uzbek and Hazara arn't ethnic Afghans. Thus the demand to change the name to Khorasan. On the other hand Afghanistan has 12 million Pushtuns , Pakistan has 28-30 million, more than twice. Hence Afghanistan can't claim to be land of Afghans in a true sense, thus their hatred for Pakistan since its inception is visible.
The best solution to future of Afghanistan would be that it is managed through a mandate system by regional powers. Tajik and Uzbek areas should be managed by Tajkistan, Uzbekistan and Russia. Pakistan should get the mandate of East and South and Iran should have the mandate of its natural sphere of influence around Herat. Only then can the situation in Afghanistan be peaceful. All of this has to happen after IS is crushed , for that a Pakistan-Russia-Iran-Afghan Taliban entente is underway. Afghan central govt is a joke, with VP who is a warlord and known rapist and war criminal, nothing can be expected of it. ANA is a group of mercenaries with a high desertion rate.