I agree with you Kevin. Vulcans have strong emotions, so Spock has a hard time with his Vulcan half. As Orci&Kurtzman mentioned that Balance of Terror was the single most important episode of TOS for this movie, they will give an explanation for why humans and Romulans see each other face to face (prior to he trailer one could assume that they just had no viewscreen on during communications, most interestingly Kirk and Khan never faced each other directly in TWOK). You suggested youself Saq that they could pretend to be Vulcans, which seems the most likely explanation as no other besides a time-travel reboot story which would contradict the basic outline of the plot, the coming together of a crew.
For Chekov, pretending that he was on board the E during TOS's first season amends this problem and that in TWOK most easily.
Remains only the lack of McCoy's southern accent, which cannot be explained at all, and I understand that this point is something that annoys you; if there were a German character in Trek I would not wanna see him changed to an Austrian
But perhaps Urban's performance is so fine that it outweighs the lack of an accent (I guess it is hard for a someone from New Zealnd to emulate a Southern accent). In fact, my guess is that he will play very well, I have more doubts about Quinto.