1. Three Way Switching
What made the Original Series so popular was the three-way interaction between Kirk, Spock and McCoy. You got the story from three unique perspectives and that not only gave the story more legs, it stopped it from becoming boring. GTA V gave us three playable characters that you could switch effortlessly between. If you got bored playing as Michael or Trevor (how could anyone get bored playing as Trevor), you could change to Franklin and carry on the game. That switching made the biggest difference in the way missions were played. One character might be on sniper duty, another is the getaway driver and the other goes in shooting. It really mixed up the missions as at any point you back was up against the wall, you could switch to someone else and change the dynamic. And as each character felt different, it kept things fresh. Star Trek: The Videogame let you play as either Kirk or Spock but you couldn't switch between the two, and there wasnt much difference when you did. So a GTA V system between three characters would make beaming down to Away Missions so much more fun.