Just a guess, but try using CfgIdentities to set up an identity with a voice Male01EN. I believe the Male**EN voices are for US units in OA, so they may be able to converse in Takistani. Read also about setIdentity.
I use a similar method to get Chernarussian civilians to speak Takistani. Here is a thread that may help:
http://forums.bistudio.com/showthread.php?t=92992You would have to live with having all of your units have identical faces/voices, otherwise you'd have to create unique identities for each one.
Another option would be to just disable conversations with {_x setVariable ["BIS_noCoreConversations",true];} forEach allUnits;