I was making a mage support henchman for my melee Sovereign Life 1, cook, and bard planning to use books to add extra magic.
After designing the henchman I decided to make him a her and clicked female. I then ended up with a normal unit with the above traits and no influence cost.
Playing around I discovered that you can use the male or female buttons to give henchmen only traits to normal units.
Nakisisa