When using "addWeaponCargo" or placing the NATO Support Box ("Box_NATO_Support_F") as Zeus (important!) you're able to equip the "MineDetector" as secondary weapon. Or every other item that uses:
class Test: ItemCore {
type = 4;
detectRange = -1;
simulation = "ItemMineDetector";
};ammo_box addWeaponCargo ["MineDetector", 1]
-> MineDetector has no weight and can be equipped as secondary weapon.
ammo_box addItemCargo ["MineDetector", 1]
-> MineDetector has weight and cannot be equipped as weapon.
or
Placing "Box_NATO_Support_F" as Zeus
Another issue is that when you pick up Mine Detector (or any item inheriting from that, in mods for example) via Pick up action (in mouse wheel), the item will simply disappear and leave an empty GroundWeaponHolder"
Via Inventory Dialog it works fine though (both by pressing hotkey or action menu->Inventory), bug here is "Pick up action".
ammo_box addWeaponCargo ["MineDetector", 1]
-> MineDetector has no weight and can be equipped as secondary weapon.
The mine detector spawned in that way still has no weight, but it no longer can be equipped as secondary weapon.