Thank you for the feedback. Adding a backpack fixes several of the
item addition failures, giving the result below. I have updated the
uploaded mission file with this change.

Using addWeapon on Binocular-type items causes the command to succeed,
but there are problems with adding e.g., NVGoggles added via addWeapon
(see http://feedback.arma3.com/view.php?id=4809).

The difference between alive and dead units still remains; the primary
problem appears to be adding various item types to dead characters
(using addWeapon does not change this).

alive failures:
Binocular(addItem)
Rangefinder(addItem)
Laserdesignator(addItem)
Zasleh2(addItem)

dead failures:
ItemWatch(addItem)
ItemCompass(addItem)
ItemGPS(addItem)
ItemRadio(addItem)
ItemMap(addItem)
MineDetector(addItem)
Binocular(addItem)
Rangefinder(addItem)
NVGoggles(addItem)
FirstAidKit(addItem)
Medikit(addItem)
ToolKit(addItem)
Laserdesignator(addItem)
Zasleh2(addItem)
muzzle_snds_H(addItem)
muzzle_snds_L(addItem)
muzzle_snds_M(addItem)
muzzle_snds_B(addItem)
muzzle_snds_H_MG(addItem)
optic_Arco(addItem)
optic_Hamr(addItem)
optic_Aco(addItem)
optic_ACO_grn(addItem)
optic_Aco_smg(addItem)
optic_ACO_grn_smg(addItem)
optic_Holosight(addItem)
optic_Holosight_smg(addItem)
optic_SOS(addItem)
acc_flashlight(addItem)
acc_pointer_IR(addItem)
optic_MRCO(addItem)
muzzle_snds_acp(addItem)

I am reporting this _because_ it is a mess, so that it can be
cleaned up and fixed.