Another call back to it is Khan's "You can't break rules, how can you be expected to break bones" speech. Kirk and Spock are both evolving--growing up. Kirk has to learn that you can't always take risks, you can't let your emotions control you, that rules exist for a reason, he needs to be more mature, more serious. Spock has to learn that you can't stick strictly to the letter of the rules a 100% of the time. You've gotta take risks, sometimes act on your emotions. That sometimes doing moral things mean not following the rules. That would have rocked. Put her in the center-seat, and just have her own the scene.