Light or Dark magic.

Usually, the opposite is used: an army of Academy units controlled by a Knight.

Hmm, I think academic armies without mini-arts and support from a mage won't last long... Have you tried this in practice against other players? The only advantage of this choice is a certain element of surprise for the enemy. As for the advantage of a mage commanding humans, one can note the high chance of a Light or Dark mage appearing and the large amount of mana for mass spells and supporting their units with regeneration, resurrection, vampirism, and confusing the enemy with berserkers and other delights from the arsenal of darkness.