I would definitely like to see it in the prime universe. (The J.J. Abrams movies are fun but I prefer the Trek I have history with.) I would like to see it on a starship. Maybe a cadet ship with some experienced crew and command but trainees (ala wrath of kahn enterprise) Maybe have someone from one of the Trek series as Captain. I would like to see them explore the remnants of Romulus and see what happened to the Empire after its destruction. I would like to see more exploration of the Alpha Quadrant. By the end of DS9 you would think we had explored it all. I remember in one of the TNG episodes of first season, saying we had only explored 14% of the galaxy. I doubt we covered the rest of the alpha quadrant in 15 years time.
I wouldn't mind seeing Starfleet with a new propulsion system that's faster than warp. Maybe a new transwarp drive that works. I would definitely like Ira Behr to produce it.