My mum's comment on this week was that she doesn't get why the dollhouse doesn't just kill Ballard and I have to agree with that.

Maybe they're afraid of causing too many questions, but, yes, killing Ballard, especially now that he's discredited seems to be the best option. Maybe they think he'd make an excellent candidate for a doll and rather trap him agreeing to join the Dollhouse much like they trapped Caroline. He certainly is hot enough.