there's a setidentity command in the comref
units init field entry would be
Unitname setidentity "Cpl_Blimp"
or failing that it could be
Unitname setidentity "Cpl Blimp"
and the code that needs entering in the Description.EXT would be
class CfgIdentities
   {
   class Cpl_Blimp
      {
      name = "Cpl Blimp";
      face = "Custom";
      glasses = "sunglasses";
      speaker = "Adam";
      pitch = 1.00;
      };
   };
Thats how the syntax would work for the setidentity command, however i have never tried it