Tell you what, maybe the third film should be the run-up to a Klingon/Federation war, and things are not going well for Starfleet. But a group inside of Starfleet and the Federation government feel that the Prime Directive is not enough so they introduce more draconian laws and measures for the Federation's safety and protection. It would be an opportunity for tension and suspense without a plot twist or action scene every two minutes, something which seems to be lost in many film directors these days.
Then the fourth film could be the war itself and how the Federation eventually prevails against the Klingons. The fourth film would have to be three hours long to do justice to some of the war's chronological events. Then comes the fifth film and it addresses the Federation and Starfleet's descent into tyranny as laws introduced in the war are not revoked. I can imagine the fifth film's climax is Kirk and a whole bunch of Starfleet captain's deciding to go rogue with their ship's and crew on the basis of moral principles and not wanting to be part of some kind of totalitarian state.
So we have a trilogy, lots of opportunity for drama and angst, action and a plot which will satisfy the casual audience, the Trekkies and those wanting something a wee bit thought-provoking. A trilogy of films all released in the space of two years and actually doing something really different with this universe.