To get a turret spotter to appear on a vehicle you will need:
1. The binocular and turret_spotter lines within the ABP.
2. A vehicle that is actually rigged to hold a turret spotter.
3. Add the turret spotter within the ebps/crew_ext and enable.
I believe the Churchill can already have a turret spotter in vanilla so look at what the devs did there.
Add this into the Stug ABP and the required hardpoints and actions to enable it.
"..\\..\\..\\common\\vehicles\\crew\\pintle_mg34\\pintle_mg34",
-
#Steam AliasWL%Streak
- 1.25334.882+1
- 2.271110.711+9
- 3.584398.595+3
- 4.247134.648-1
- 5.248150.623+9
- 6.19165.746+4
- 7.911555.621+1
- 8.423.933+2
- 9.790538.595+9
- 10.18577.706+1