Barbarian King during Defense Mode
I just got my barbarian king level 5 and I just enabled his ability (Iron Fist). This ability has no cost during attack and specially no cost for the summoned barbarians when activated.
In the opposite scenario, I have been attacked many times and the Barbarian King automatically respond to defend the base. I have been always outnumbered.
I would suggest that when Barbarian King is in Defense Mode, He must automatically activate his Iron Fist. Let us say when He was outnumbered by more than 5 attackers or he has been damaged by 75percent, the Barbarian King must activate his ability to further add to the base defense.
This feature would be available during clan war and/or regular base.