Since Afghanistan is land locked, Pakistan should go out of it's way to allow duty free commerce thru it's Gwadar Port into Afghanistan. The two nations can work out a commerce treaty with a simple percentage of either gross or net revenue of all such commerce earned by Afghan businesses and/or the Afghan government.
Separately, Afghanistan would do well to develop a similar commercial treaty with Iran.
Pakistan is not the only key to the land lock of Afghanistan.
However, if situation arise, when other 4 border countries of Afghanistan would build iron curtains, than conditional transit may be allowed, minimum conditions as following.
Conditions:
Officially, contracted as '
Jinnah Transit Aid'.
No arms or military related equipment be allowed to transit.
Security deposit:
To start with, Afghanistan should deposit a security fee of $10 billion.
reimbursement of expenses:
Pakistan should levy a (minimum) charge $5/kilo port processing fee, for all sort of transit.
All transit should be duly, inspected and marked, to avoid misuse of transit.
Import surcharge:There should be a $1/kilo import surcharge, which may be written off, depending on Afghan co-operation in trade with Pakistan and foreign affairs.
Strategic surcharge:
All
consumable items be exempted from strategic surcharge and should be stamped as a
gift of Pakistani nation to Afghan nation.
There should be $1/kilo strategic surcharge, for all non consumable items and all shipments, materials going beyond Afghanistan.
There shall be $2/kilo strategic surcharge for all consumable imports from India and $2/kilo for all non-consumable imports from India and $5/kilo for all imports from India destined beyond Afghanistan.
Further following surcharges can be added depending on calculated expenses:
Security surcharge, Environmental surcharge, Infrastructure surcharge etc.
Penalties:
If any stamped/marked/recorded, transited stuff ever found in Pakistan, than Afghanistan be made to pay penalty of $1 million on every such occasion.
If Afghanistan, try to import defense related material, it should be fined $5 million on each such discovery.
If an evidence found of Afghan involvement in terror activities inside Pakistan , all of their transit shipment within Pakistan borders and at ports, be confiscated for good and shall be only resumed once all of Pakistan's security agencies give clearance.
In case, when Afghan govt. issue anti Pakistan statement or its press print anti Pakistan report without prior approval of defense, interior, foreign and trade ministries of Pakistan, half of its security deposit should be confiscated and if Afghan regime found conspiring against Pakistani interest in partnership of second country, all of the security deposit should be confiscated.
Further transit aid be halted, until Afghan regime offer official apology, and pay an allocated fine to cover damages, last but not least re-new $10 billion of security deposit.