While centered, you are considered to be wearing Heavy Armor for the purpose of the Sacred Defender tree, and may use your Charisma score for Attack and Damage with Ki weapons.
Notes
This feat does not apply with empty weapon slots. For unarmed combat, you must be wielding Handwraps for this feat to work.
Bug: The tooltip still names any religious class as requirement. This is not possible, since the Follower of the Path of Light feat is exclusively for Sacred Fists.