If N had planned to meet up with Ms. Cope outright, there would be some record of their correspondence. As some articles have already noted, computers were seized from her residence. Also, the police have her cell phone. If a meet up was 'planned,' there would be some electronic trace of it, and It follows that a suspect would at least be named by this point. However, this hasn't happened, so I consider that theory secondary.
Riddle me this: if you were planning an abduction, would you plan to take that person from an airport, where risks would be at its greatest? Would you hinge your entire plan on stealing your potential victim's car, and praying that the vehicle was well enough off to make your getaway? Seems to me like that's putting a lot of faith in factors entirely outside of N's control. And, for the record, typically when crimes are committed, particularly kidnappings, the attacker wants to be in control of as many factors as possible.
I believe this lends support to the theory that N may be somewhat familiar with the airport's layout. Maybe N is an employee, or former employee? Maybe he/she casually knew Ms. Cope? I do believe that Ms. Cope was selected as a target because she was walking through the airport with her car keys visibly in hand. N would have seen her with her keys and no purse, and could have easily concluded that she was heading to her car (why else would she be walking through an airport with her car keys in hand?).
Because Ms. Cope left her work station sporadically, and not habitually, I think it's unlikely that N planned the encounter specifically for her, unless he intended to seize her when she left work, and just decided to take her sooner when the opportunity presented itself.
But at this point, there aren't many -- if any -- major updates. This is surprising to me as it's been established as fact, according to MSM, that Ms. Cope was actually physically present at an airport and gas station, both high-profile areas with lots of security and surveillance.