Given the rules wording, we (Wayne and I) have always used ANY units. The rules do not tell us it is personel or ordnance only and you are right, not only are they neither personel or AFV leaders, they are simply not leaders at all.
I'll go with that and makes for quite a mental image of the Kommisar leaping atop this T-26, opening the turret and shooting the crew after it failed to recover!