The challenge will be to find a way that they can have a base game that is offering a good set of features while leaving room for future DLC.
I think they should strive to offer a wide range of basic features and then future DLC can expand upon those features, like offering new ways to play and create with those features. This will give them more options when making DLC and new worlds.
The game should offer better management features too like for example offer ways for the player to assign roles to sims and controlling them more easily so they could make future DLC like Restaurants and Hotels play better.
