So as 'obedience' rework' going on I wanna give some info on the future changes as they will involve most of the stuff involving servants.
Firstly, there's Will. New Will is basically a girl's rank. High Will indicates big potential, however it also makes obedience maintaining harder. Basic idea is that obedience is built by your actions, but reduced by will power of a girl. That means, that breaking her will would efficiently result in making girl easy to control. However with building obedience through many means you will also break her will, impact her personality and make her worse by comparison. At least this is what gonna happen at the start.
On the opposite side of scales lies loyalty. Building loyalty is considerably slower and harder but it will outweigh willpower and allow you to have constantly obedient girl with strong personality.
Next, there's introduction(or actually implementation) of 'corruption' stat. Corruption refers to girl's acceptance for deviant actions. If you force her to do something and corruption is not enough for her to accept it naturally, she takes penalty to Will and her corruption grows in the process. Corruption also plays another role: new mana-for-sex-system will either scale from girl's loyalty or from her corruption, depending on which one is higher.
This is the basic layout on what will be going on in the next version.