Lumon industies (and/or Milchick) probably has all sorts of crazy ass cult company reasons for hiring a child, but I fully believe the main motivation for hiring Miss Huang was to discourage innie violence against supervisors.
Since, you know, Dylan G had no reservations and regrets over biting Milchick (and tearing through skin).
Not to say that her being a child would prevent everyone from dropkicking her one way or another to reach freedom *cough* Helly *cough* but hey gotta give it to the Evil Corporation for coming up with a pretty solid plan. It would've gotten me.















