I think I have a idea. What if Shatner does not appear in the movie because Nimoy was approached first and demanded so much money that they couldn't afford both and Nimoy demanded a script that was specifically writen about the Spock character and would not participate otherwise. Say we have a script in which the Romulans have captured old Spock during Reunification while he had gone underground. The Romulans use a mind device or other things to probe his mind for a way for them to go back in time to defeat the federation abd destroy Vulcan. As the torture continues we see Spocks past where the Romulans are focused on a specific mission on the Enterprise where young Spock and Kirk or Pike are revealed to us. At the end of the movie old Spock sacrifices himself and defeats the Romulans plans. Shatner passed the torch to the Next Generation and Nimoy passes the rorch to the future generation of the original Enterprise. That could be a distinct possibility huh?