Nice, simple, easy to use. Might I recommend allowing users to double-click the weapons and items to add them to the crate?
I would also recommend that you use
while {alive _this} do {};
So it would look something like:
while {alive _this} do {
// Settings
_this allowDamage false;
_weaponAmount = 4;
_itemAmount = 5;
_magAmount = 34;
_sleepAmount = s; // 'S' is the amount of sleep time the user has selected
//Clear box
clearWeaponCargo _this;
clearMagazineCargo _this;
clearItemCargo _this; //to make sure box is empty of everything
clearBackpackCargo _this; //to make sure box is empty of everything
//Add to box
_this addItemCargo ["item", _itemAmount];
_this addWeaponCargo ["weapon", _weaponAmount];
_this addMagazineCargo ["magazine", _magAmount];
sleep _sleepAmount;
};