> Skill development and various activities like bowling or repairing as in-game mini-games.
> Detailed nutrition needs and nutritional properties of different foods.
> An organically evolving town with buildings and houses that appear out of zones like in Sim City. (This could be accomplished by having a large selection of pre-made buildings that can appear out of zones.)
> A more open sort of real estate, your character could be homeless or live out of motels.
> Placing wires and pipes when creating your house, and a detailed physics engine for buildings houses. For example, building a house that's too top-heavy could cause it to collapse.
> Careers that have a real impact on the game world- for example, a politician would have control over what parts of the town are zoned.
> Furniture that is ordered out of furniture stores or in-game catalogs without entering "buy mode."
> Various religions and ideologies that affect what your in-game character can do without a guilty conscience.
> Violent accidents and murders
> A simulated in-game stock market and economy that influences food and item prices as well as rent and wages, and that is influenced by politicians and businessmen.
All of these features have been explored in various different games, but they've never been put together into one ambitious life-simulation game. The Sims could be so much more then a digital dollhouse if the developers cared for anything other then endless item-pack DLCs and meaningless amusement-park-ride style items and rabbit holes.
Think of the lock-picking game from Skyrim, the fishing mini-game from Stardew Valley, the complex machines of Factorio, the economic and societal simulation present in Tropico, the nutrition simulation of Unreal World, the gamified learning of Duolingo, the religion and government types of Crusader Kings II- all these things and more could be combined into one game if a studio was ambitious enough to undertake it.
