Gift of 'Unreason'

[Panpiper]

I am looking to create a 'ritual' spell that turns a commander type into a troop type, robbing them of their commander status. Looking through example spells however and the modding guide, I see no clue as to how to achieve this effect. The idea would be to allow the player to pad his troops with units possessing commander stats (like sacred commanders which could be built outside of the capital).

Would anyone have an idea as to how to achieve this effect?