Interchangeable World Generation

A function could be added that allows the player to build structures in a "Flat World" setting. Once the player is finished building, they would be given the option to "Generate Terrain". This function would generate a standard map around the pre-existing structures that the player has made. This would provide opportunities for the character to build on flat surfaces without hours of preparation, while also allowing the player to alter the newly-generated surroundings until it's just right. Although, admittedly, I do not know how to preserve changes to terrain if they decide to build additional structures. Thank you for your time, consideration, and inspiration. - A Loving Fan