1. A Fourth Character (Extended Story)?
I personally thought this GTA V story was shorter than most and that it could've been much longer. You may disagree but I think the game could benefit from an expansion pack (a year or so down the line). How about a fourth character? He may have nothing to do with either of the established protagonists. He may be friends with one of them - Franklin? He's young and rich. He might get bored. He could maybe even be some kid starting from the bottom and going to one of the three protagonists for missions and jobs. I definitely see an expansion pack coming that gives us another story or extension to the current one - it's merely a case of 'when' and not 'if'.
That is it from me, I can't think of too much else I want. Online seems to have sorted anything I wasn't too sure about. What about you? Let me know what you want to see in a GTA DLC or expansion pack below!