I think you are over thinking about this.
According to me this "follower" is just here because the paladin can become an oathbreaker.
The game needs a NPC to explain that + to allow players to change their oath again.
I just hope he will not stay in camp after act 1. Some choices should be definitive at some point and I guess you cannot be an evil paladin indefinitely and pay to become good again when it suits you.
In the DMG, the guideline is no more than twice (Paladin -> no remorse oath breaking to Oathbreaker -> atone to Paladin again -> no remorse oath breaking to Oathbreaker), but in the guide the requirement for Oathbreaker is more than just breaking an oath. The player character has to shown no repentance for his actions and his alignment has to be evil. Still, if you can pay Mr. Knight to return to Paladinhood once you selected Oathbreaking, they could limit it to once and the next time you break an oath and decide to go Oathbreaker it is permanent (someone will mod it out, ahahaha).
