Get fully unlocked with the tanks and you have the option of the 3rd seat in the tank, the laser targeter. Not the range of the soflam but still a very good option to have.
Always have the javeiln equipped when in a tank in case i swap seats, someone else occupies the 3rd seat, get out and javelin the crap out of whatever has been lit up. Doesnt always happen that way, depends on your squad / team mates.
Always check with the driver of the tank what unlocks they have got, swapped over seats a few times because i have reactive armor and the original driver didnt.
stuff like that you need voice chat tbh..unless playing with mates