The Federation enters a cold war with the Romulans after the Dominion War and rebuilds its fleet. Many new officers are pushed out of the nest to fill necessary positions, mixed in with experienced personnel from the Dominion War. This rebuilding includes more warships (a la the Defiant) and a return to including Marine detachments for certain ships.
The Klingons enter a formal alliance with the Federation with Martok as Chancellor, Bajor enters the Federation, and the Cardassians enter their own rebuilding phase where the provisional government is split between three main parliamentary coalitions: pro-independent Cardassia, pro-Federation, and a pro-Romulan faction that wants a return to the Cardassian Union pre-Dominion War. The Federation is still cleaning up Jem'Hadar holdouts and Vorta-turned-warlords all while patrolling the Neutral Zone to keep the Romulans at bay (who have a numerical advantage and are cunning as ever). My fanfiction stories are the missions of one of these new ships commissioned to clean up and sentry duty, mixed in with standard Trek adventures and political intrigue (especially with the Cardassians).
The final story is supposed to be a new president of the Federation winning an election based on "going back to the way things were," scaling down Starfleet operations, the ship getting decomissioned, and the crew reassigned.
I will take my autism stickers.
Edit to add: I ignore Nemesis (which has the Romulan supernova and abolition of the Romulan Neutral Zone) and I ignore everything after Enterprise.