I want to lay the foundation for my potential plot to Star Trek XII. It should mix comedy and drama.
Five acts each with a climax and the resolving climax at the end of act five with no cliffhanger. Here I will reveal the first act.
Act one
Starfleet academy where we meet the antagonist; Admiral Odin we will call him for now, where Kirk among other Captains are hearing that the Klingon Empire is on the verge of declaring war on the Romulan Empire over the Rura Penthe incident where forty-seven Klingon war birds were destroyed by an escaping super ship of Romulan origin. The federation doesn’t want a war in this quadrant of the galaxy and is offering to mediate between the two Empires to try and prevent a massive intergalactic conflict that would see billions of lives die.
I like that you take up events from XI - that there are some consequences to those events. Also, having Romulans and Klingons (and Cardassians) in it is always good
On Admiral Odin are main antagonist. We establish that he is well respected and a hero to Kirk, a real father figure to him. Odin has been ordered by Admiral Nogura who is the head of Starfleet and the President of the UFP to head a task force into neutral Cardassian territory to; planet X we will call it for now, with Ambassador Sarek to negotiate a peace treaty between the three major powers. Admiral Odin could be played by, perhaps some previous actors of ST captains who we would be attached to emotionally: Patrick Stuart or William Shatner, we could choose characters of gravitas like Christopher Lee or Ian McKellen, or perhaps someone younger like Viggo Mortensen or Liam Neeson. I am going to lean on Shatner for this role for now.
Continuing act one.
Liam Neeson would be good. I doubt that they'd cast Shatner in RL because they think fans are so dumb they'd think he'd be a time-traveling Kirk.
Kirk takes aboard the Enterprise Ambassador Sarek where Kirk explains to the officers that the USS Enterprises role is purely to wave the flag for the fleet. We will see everyone from the cast of XI reintroduced. Admiral Odin aboard his old Dreadnought the USS Ardor is seen with the rest of the fleet. Kirk orders the Enterprise to go to warp and Sulu gives an estimated ETA to planet X as five days at warp 6, so we establish that planet X is isolated deep in Cardassian space.
Character points, Spock should eat dinner with Uhura and we should establish that Uhura and Spock have their own quarters but Uhura is discussing moving into Spocks. I think that Spock should discuss the merits of the mission and his doubts about achieving its goals with Kirk over a game of chess.
Agreed on Spock, Uhura, and the chess-game.
The Climax the Enterrpise comes out of warp to discover that the Cardassians have attacked the Klingon fleet of warbids with the help of another fleet of Dreadnought class Federation Starships who reveal themselves to be under the banner of Admiral Odin. Kirk contacts Odin aboard the Ardor from the bridge demanding an explanation. Odin replies he did what was necessary with the Cardassian’s by destroying a significant threat to interstellar peace in the form of these huge Romulan and Klingon armadas, first with the Klingons and now they must intercept and destroy the Romulan armada now on its way. Sarek calls Odin a traitor. Odin orders Kirk to go to warp to ambush the Romulans who are uncloaked and on their way to planet X. Kirk pretends to agree, attempts to order the shileds on the USS Ardor down which fails and the USS Ardor opens fire on the USS Enterprise. Kirk knowing that he is overmatched by odins fleet orders all loyal federation Starships in his fleet to go to emergency warp at once laying in a course to the Romulan armada on the way. Many go to warp with the Enterprise but some are destroyed in the attempt to flee. The old Dreadnoughs can only travel at warp 6 while Kirk’s fleet travels at Warp 8 escaping the Dreadnoughts and buying Kirk and crew some time to figure out what to do next, so far away from contacting the UFP and help.
I think Odin is revealed too early. We should only see a strawman here - and IMO a Vulcan would be perfect (but then the first party to arrive - and to be attacked - would have to be the
Romulans):
* The Vulcans are emotionally compromised - they want to take revenge on the Romulans. Remember Spock's reaction to Kirk's offer to help Nero at the end of XI? I think Surak's teachings are being questioned by a lot of them now. It would tie in with the destruction of Vulcan, showing the consequences of that part of XI.
* The Vulcan could argue that he's doing what's logical - the Romulans have proven to be a threat that can strike at the very heart of the Federation (= destroying Vulcan, attacking Earth). This threat must be eliminated. The logical consequence is to prevent the Federation to placate the Klingons and Romulans, and giving the Klingons an advantage by weakening the Roms.
* Since the Romulans will certainly react to this betrayal with a declaration of war against the Federation, we'll suddenly find ourselves side by side with the Klingons. An alliance made in hell, but will please the Klingon fans out there

* Sarek/Vulcan Traitor-interaction should be fascinating - a battle of brilliant minds, each convinced their way is the right way and being able to argue logically for it

* That a Federation Admiral is supporting this scheme should be the big shocking revelation towards the end of the film. You close with a bang, not a whimper.
So the next part of the story, act two will establish that somehow Kirk must reveal the treachery of Admiral Odin to the Romulans, prevent a war with the Romulans and perhaps also a civil war within the federation.
And the threat of civil war would be so much more dramatic if it would be started by a whole
people, the very people who were humanity's mentors when it made its first steps into space.
Kirk and crew must warn and negotiate with a violent race of conquerors in barely a days time IE use diplomacy with Sarek‘s help. I want us to establish some things about the Romulan culture while we are at it.
Oh yes, me too! And I want an official Romulan language i can read my Shakespeare in, dammit!