I personally love game worlds that are open and let you interact with the world. It's fun to do something and see how the AI responds to it. More than that, it would be interesting to see the AI controlled persons actually living in the world and interact with it just like you as a player do.
I did my fair share of game programming as a kid and teen, and often I was interested in creating an open world where you could do anything you wanted - sort of like what some rogue games were like. However there still haven't been a good game like that, even not in MMO's where it would be more viable to do. I think EVE and Haven & Hearth (still alpha version and technically not that good) are probably closest to that, but I'm not personally so interested in space or fantasy setting, and after all they're MMO's and not playing around with the AI so there are scalability problems. But why do all the MMO's and other RPG games deliberately concentrate either on 1) fantasy setting 2) space setting 3) crashed world (Fallout, I'm looking at you, even while you're a great game) 4) mindless shooting (CrimeCraft). I know games are used to escape our every day activities, but it's not like you couldn't do so even if the game world was based on our time.
I miss the days when games tried to create an environment where you could do or play however you wanted. Rogue-likes, SimCity, even Baldur's Gate. The last one had an quite open world even if it was story-based. I could go to a pub and find interesting people there or just hang around, or find an underground thief guilt and try to join them. I never finished those games (Baldur's Gate 1 & 2) but I played them a lot, because I liked the city setting and the environment.
As a kid there were a few occasions when I skipped school and just walked around in the city and surroundings. It usually gave me nice ideas for a game I would create and how the AI would interact in it. Every person in the world needed to be persistant and have a name, job and different relationships with persons. You as a player wouldn't be overpowered, but just an another such person in the world. The interesting thing about it would be that since you have relationships and jobs with persons, you have a certain level of control over them. They need to get food and other things like furniture and fulfill their needs, just like in real world. For that they need a job.
If you had a business plan in the game world, you could hire those people to work for you and assign orders for them. You started a bus company? You assign persons to drive certain routes every day at certain times. Other people, controlled by the AI, need to get to their work places so they look for the best route there. Do they own a car and have cash for fuel? Then they use that. If not, look if there are buses nearby. If so, use that and you as a bus company owner would get in-game income. If you were an asshole towards your workers, they would grow hatred towards you and maybe even destroy your property (ie. items or land area owned by you).
If you needed to build an house or building, you would get people to do it or help you. The land tiles would be leveled and building blocks would need to be bought and carried over. Once finished you would be the owner of the building and could even rent it to other people. Simple rule like "pay x amount month and this is your property". With a network of inter-connected needs the person does it's best to fulfill those.
Of course I would like to develop an AI that could do all these things on its own, instead of scripting based model or something where the AI has to cheat to work. I know it's problematic in real-time especially with a big world, but if you have a turn based game those rogue-like games, theres plenty of time for the AI to calculate. On top of that, it doesn't even need to calculate it when turn is switching - you can have a separate process calculating what the AI will do constantly, even if its your turn and you're just idling or in your inventory and so on.. Then AI controlled people will be ready to do their choices on their turn. I think The Sims takes a similar approach with the processes and it could even work in real-time - we as humans aren't that good with impulse thinking but usually think things for a while before doing them, like should I buy a house or break up with my girlfriend, or start a company.
If you know games that offer such sandbox environment, or can think of what would be the problems with such AI or game, please comment.