I've long wished to read Nimoy's story notes on the script. There were changes he wanted done before he'd agree to direct, but Berman wanted the script shot as written.Both Spock and McCoy lived to interact with members the Enterprise D.
But "Generations didn't explore that aspect. It's precisely why Nimoy turned down the role. "Unification, Part II" had put Spock into the thick of the action and provided cross-pollination advertising for ST VI, which he had produced. "Unification, Part I" had a cameo of Spock only to split the salary budget across two episodes and make him more affordable. Kelley did McCoy in "Farpoint" for scale, as a special favour to DC Fontana and the fans.
No script put Spock or McCoy into the heart of the action.
If it were up to me, I'd have contrived a way to get Spock into the 24th-century part of the film. Doing what exactly I don't know. That may or may not have been one of Nimoy's notes.
But my ideal rewrite would put the climax of the film on the Enterprise-B. Have Kirk and Picard leave the Nexus and stop Soran at the very beginning. And you'd have to contrive a reason for that -- maybe Soran himself has gone there to try and drive the Enterprise into the Nexus to reunite the split halves of the saved El-Aurians. I doubt that was one of Nimoy's notes.
