I think following stories, like Walking Dead games (from Telltale Games) and Heavy Rain (from Quantic Dream), would be fun because it can show further stories of GTA universes and players can select whatever they want.
GTA franchise is basically action-adventure game so it focuses on actions, of course, but therefore there's not many place for storytelling. That's why I'm thinking about GTA as interactive story game.
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Well I'm super busy for now because of my main work (in real life) so I cannot suggest many ideas, but if I say:
[1. Numerous protagonists]
We can control many characters and decide their fates, that's the one of main features of interactive story games. Like GTA IV and GTA V, some of them will meet each other and decide whether they cooperate or confront.
[2. 'Remaking' old characters from 2D&3D to HD]
somehow characters in 2D&3D universes are described as silly and it makes old series worse (in storytelling, I say). So in my opinion, I'll import and remake them in HD Universe for their better background, personality, motive, etc.
[3. QTE and choices for storytelling]
Main contents of this concept, as I said in (1). Because most interactive story games are not open world adventures, they must act with QTE in nearly everytime. However, because of it, QTE can shows sequences including serious dialogues and dynamic actions.
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At first I tried to write script of 3D Universe remake as film or TV drama, but they can't reflect watchers' choices, you know. That's why I changed this to interactive story games. (In fact, game 'script's. I'm not a game developer)
What do you think? Any ideas?