What Afghanistan can do to promote Persians is very simple. Afghanistan should insist on regional trade with Persian speaking Khorasan province next to Herat and avoid direct Kabol-Tehran trade relations. Khorasan will become a powerfull ally of Afghanistan in Iran. Industries dealing with Afghanistan in Iran such as car industry should be moved to Khorasan instead.
Pakistan being very concerned about the emergence of Khorasan as a counter force to Pakistan on the borders of Afghanistan has dispatched the Pakistani Prime Minister and the Pakistani Foreign minister to Khorasan to meet with high level officials in Khorasan. This is the significance of Khorasan for the future of Afghanistan.
Afghan policy should be similar to other countries in the region. For example the Republic of Azerbaijan in north west Iran is promoting the interest of Azeris in Iran. It constantly talks about "Persian chauvanism" and "lack of rights for Azeris" when Azeris themselves are actually running Iran. Turkey has the same policy in Central Asia. Afghanistan should also start talking about Persians in Iran and start promoting Persians as a minority group living under Azeri Turkish rule.