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",
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#Steam AliasWL%Streak
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- 7.323143.693-1
- 8.854232.786+1
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- 10.325117.735+2