Regarding Claire:
Her going from a zero controll position (and "broken" state) to a with "full" controll, could also led to her willingness to "missuse" this power. If William (both forms or other) will annoy her, perhabs she will think, that they are needed for a "reminder" who is controll and who not. If this hold on her inner personality will be testet and some of her inner values and thershold could be changed over time.
This could escalate on route that even engulf herself and end with a mindset Claire herself (or the MC) never wanted - perhaps to a point some more powerful source must direct intervene.
Or if she has full controll over William without reason or consequence to fear, she bound to be a saint, if she never use/misuse her new status.
I truly believe a furious Claire could be the end of a toothless William or Janice. Just broken free from her chains and enraged against her better judgment with the Antichrists support things could get ugly pretty quick.:evilsmile:
As always, only my two cents.