That's kinda the point though. This is supposed to be something new. Nimoy is as much a part of the past as Kennedy and Armstrong.
Hands up anybody who'd recognise Pine's voice?
Anybody? Anybody? Bewler? Bewler? (Not you Mrs Pine)
People hear Pine deliver, "Space, the final frontier...." Fans will figure out who it is in a moment even if they've never heard Pine before. It would be the first realization that this IS something new.
I think you're missing the whole point of this movie.
It's not for us fans. Us dorks who post in here about the shape of the bridge not being like on the original therefor it's an affront to God, Kirk, and Roddenberry.
We're going to see this movie regardless of what we say. It'll be the first new Trek in 3.5 years, we're going to suck it up like cocaine.
This movie is going to be geared to make the most amount of money as possible, so it needs to reach the widest audience. Having some no body say the lines won't add any "Ah, cool. Star Trek. I remember that" to it.
Nimoy is iconic, Chris Pine is not.