The unfortunate biggest problem here is that we live in a country that is very ageist and movies are directed towards teenagers and very little attention paid to those over the age of 21.
The actors for those characters would be considered way too old. Nimoy was allowed in Trek 09 b/c he was surrounded by much younger actors in their 20s and early 30s.
There's no way Paramount is selling a Trek movie where the youngest leads are in their 50s and the oldest (Shatner and Nimoy) are in their 80s. They got away with guys in their 50s and 60s during TOS movie era back in the day b/c they were TOS with Kirk and Spock/Shatner and Nimoy, but I doubt that's ever happening again.
This idea is best left for fanfics or novels.