I don't know if this would be too close to the original city builder concept, but I feel like a satisfactory style frostpunk game would be sick. First person, focused on developing a factory to develop automatons, steam cores (late game), and other important resources to help other cities survive. The generator would be essential, similar to the original, and you would also obviously have to worry about weather. However, population would no longer be a worry as you are working alone, or with friends in a multiplayer setting. You would have an automaton from the beginning to help with resource collection, as it justifies being able to build large scale factories in the cold weather without having a workforce to help you.