I know the central question of the thread is several months old at this point, but my take on this is that there's no reason the recently assimilated Enterprise crew members couldn't have been saved as Picard was. As was mentioned, even in TNG we've seen disconnected Borg reassert their individuality and in Voyager their personalities have been returned and there have been various options to remove the implants.
Lily even points this out in the movie, that saving the crew members as Picard was saved was a possibility, but by the time the Borg have taken the ship Picard is so obsessed with dealing with the threat that he's unwilling to consider the possibility. I think it's easier for him to dismiss saving the assimilated crew members because he hasn't met anyone who has fully recovered from being assimilated. The Borg in TNG who have been disconnected from the collective don't appear to remember their past lives, if they even had any and weren't just incubated as children as in "Q Who". And so, somewhat egotistically, he assumes that his recovery is a unique circumstance. And as the movie shows, his recovery was far from complete--he may in fact have wished to have died after his assimilation.
Don't get me wrong, Picard is one of my favorite characters. But First Contact brings him to a place where he's as obsessed and out of control as he'll ever get.
I do think the movie leaves open the possibility that some of the assimilated crew members, the ones who weren't in Engineering, could be revived and saved offscreen. That post-First Contact novel would have been a great idea.
TC