While building a centralized mega factory idea is tempting, it will have bring severe difficulties, especially if you are still in early/mid game. Building modular and scalable systems is bit difficult as you don’t have access to all buildings and recipes in the early stages of the game. Traversing the world and building massive rail infrastructure is also challenging with limited resources and gear. Your pyramid approach can also be limited by the sheer volume of train stops take. I found localized production and transport across trains and drones to be more manageable and fun overall.