I personallly think (or want) Sam Alexander as Nova with a story similar to Ghost Rider's story.
this would be my idea:
Richard Rider travels to earth after escaping thanos's attack and meets Sam Alexander.
He then decides (because of his injuries) to give Sam his powers before he died.
that would be my idea for him.
Do you think that's likely or do ypu rather belive that Richard Rider is becoming Nova?