Plain and simple, what features have you wanted R* star to put into a GTA game but haven't.
-More gore and realistic body damage.
-Weather that affects the game.
-Better stealth mechanics(Splinter Cell, Hitman, Watch Dogs)
-More in depth customization for cars, guns, players.
-More side or random missions that keep you from continuing the story.
-Realistic police response haha
-More enterable buildings that are important or have some use to the player.
-More action( I hate that after a GTA game is beat all you have to do is drive around, shoot a cop here and there, I want gang shootouts, and fight competions, and Hitman missions).
-More randomness, have crimes that occur that are more violent than muggings, like mini-heists or shootouts, and let you be the hero or join them and help cause more chaos!
-More gang life, parties, racing,fighting, just random gang stuff.
-Deadlier gangs, like Russian mafia or Mexican cartel.