I want to design a game that takes the player through the life of a girl with an extraordinary power that sets her apart from the people she meets...
in early life she set herself apart by not knowing she could see something others could not, but was sheltered by community leaders that understood the validity of her observations despite lack of visible evidence. Once those leaders are made unavailable, or she leaves the community, she discovers her insights are neither common nor widely appreciated and could be completely misinterpreted if not used carefully. The player must then choose how they wish to interact with numerous people using these insights to achieve her goals, one step at a time.
her journey starts in her home town, on the edges of a great forest filled with natural wonders and hazards. Scouts uncover an increase in hostile mutations, and her mother is brutally assaulted. When she finds her mother, alive but weak and delirious, her second sight is inadvertently drawn in to her mother's consciousness, affected by foreign energies, and pulls her out of her stupor. For this display of extraordinary ability, she is granted a selection of opportunities for her future outside of the town.
Each of those choices are presented to the player as offering different styles of game-play and additional playable characters. At this point in the game, there are already several different possible outcomes based on the player's choices. Have they killed anything? Did they help any of the villagers? How helpful were they? Did they stand still while talking to people, or did they pick up everything that wasn't nailed down? It should be made clear that the main character is the player's avatar in a realm of people with unique perspectives, and their choices will affect those perspectives (despite being 100% programmed.)
A truly advanced game would involve some kind of AI that could form its own opinions and reactions, but I don't foresee that as being possible (or playable) any time soon. I believe responses to player actions should be predictable to players with enough experience interpreting the reactions of other people. As such, the most important development point of this game would be the NPCs' expression of emotion to the events in the game. These things are typically developed first by writers, and then by visual artists and voice actors with the assistance of a director.
This is not to say that the game-play is any less important, but if the objective is to achieve an outcome through character interaction, the rest of the game-play should simply be a chance for the player to reflect upon the interactions they've already had. I would not force these reflections upon the player; having what is supposed to be the main character's thoughts read to me 5 minutes after I've thought of them myself is not what I call entertainment. If a player is unable to reflect on the events that have transpired and draw reasonable conclusions in advance, they should be given the opportunity to be surprised and act accordingly, without being outright punished.
But then, how will the game differentiate between a player that is surprised by an event and one that saw it a mile away? Will it even be necessary?