I've heard some people claim that the quality of the best TOS episodes exceeded that of the TOS films. What are some TOS episodes that you think were good enough/have the scope to sustain a full feature run time. City on the Edge of Forever is an obvious choice. More things happen in those 50 minutes than happen in some entire feature films as it is. It could have been even more gut wrenching if the relationship with Kirk and Edith could have been expanded. Space Seed is another one that I think would have worked as a movie. The "set up" of the movie would have been most of the episode, with the conflict for control of the ship making up the entire second and third acts instead of just the last 15 minutes. I could also see both the major Romulan episodes as features (Balance of Terror and the Enterprise Incident), especially since Balance of Terror was actually based on a film. Maybe Mirror, Mirror too.