Interesting train of thought. The main issue I have with it however is that New York, in fact, is heavily influenced by many places around the world (the famous gridiron street system for example was borrowed from the layout of Glasgow, Scotland - my hometown) and very rarely is it the other way around. I can think of no places whatsoever in Europe that have been influenced in any way by New York, as Europe's collective history is far, far greater than that of North America (North Americans, I mean absolutely no disrespect. I mean 'greater' purely in terms of how much further back European civilizations history stretches).
I do agree that it would make sense for Game Freak to imply that a large number of Unova Pokemon were in fact introduced to Unova from other regions - such is the cosmopolitan, multi-cultural real world New York. However, I don't think too much should be looked into about the starters representing Europe, China and Japan. If it was truly an attempt to mirror the cultures that influence real world New York, it would be difficult to justify having China and Japan represented and not, say, Italy, Ireland, Mexico and the literally dozens of other countries/nationalities that have helped shape the modern day United States.
Lastly, let's not get into a habit of bunching many extremely diverse, individual countries together and calling them 'Europe' when it is listed alongside 'Japan' and 'China' instead of 'Asia.'
Which reminds me, Harimaron also needs to be nicknamed Paris (pronounced like French) 「パリ」
Oh good, I'm not the only one who's already thinking about nicknames.
I'm picking Froakie as my starter, and I totally wanna nickname it François (or Françoise it's female), because of the whole France-based-region thing. My second choice for starter is Chespin, and I'd probably keep the French naming and use Charles/Charlotte. And I don't care much about Fennekin, so I haven't really thought about names for it either.
Well you could use an external programme like pokesav to alter your savefile on black2 so that it has the key and then transfer that to white2, I think.
But I am not sure I see an actual problem in your case. Why not play Black 2 first so that you can transfer Challenge Mode to White 2? What makes White 2 more special? Isn't it better to finish Normal Mode before Challenge Mode, so that you can appreciate the differences? You can consider White 2 to be your main version either way, but arguably more so if you play it last.
Well fuck. That's a real shame...
Challenge Mode can't be shared over Wi-Fi, so you're out of luck (as are many people). The Key Link feature works via infrared.