While Binocular, Rangefinder or Laserdesignator are weapons and can be added and removed with add/removeWeapon commands, they can also:

1. be added and removed with add/removeItem command
2. returned with items command
3. returned with assignedItems command

When they are removed from assigned slot they become "items" in the inventory. So how one goes about putting Binocular that is in the inventory to the assigned slot?

addWeapon will just add another Binocular. Did I mention this whole thing is mega confusing as well?

Solution: make Binocular, Rangefinder or Laserdesignator fully behave as items. For this make assign/unassignItem and link/unlinkItem work with these items.