A couple ideas:
Kirk and Marcus get together and maintain a stable, monogamous relationship while serving aboard the Enterprise. No more "Kirk's always banging green-skinned, alien space babes on every planet", which is a bit of ascended fanon that needs to go away.
A faction of Vulcans develops on New Vulcan who wish to reunite with the Romulans, potentially jeopardizing the membership of one of the Federation's founding members. Despite the mismatch in ideologies, this group sees it as imperative for the sake of survival that the two races combine their gene pool. What's more, Prime Spock is sympathetic to this faction, seeing this as a second chance to complete the reunification that he failed to achieve in the Prime universe. NuSpock takes the opposite position, believing the Romulans as untrustworthy as Nero. The two of them end up as antagonists to one another, in a sincere, non-mustache-twirling manner, and in the process explore whether the survival of a race is worth assimilation or if the moral imperatives of one's culture trump pragmatism. In the end they find a peaceful solution (it is Spock squared, after all) and the Romulan Empire's relationship with the Federation thaws similar to the Federation and Klingons in Prime Trek.