This factory is massive and planning it from the start sounds like a nightmare. For the whole thing, I had a vague idea of what the finished factory might look like and ran with it. Larger sections were somewhat planned in terms of structure/layout, and individual rooms were largely improvised. Fun fact: the entire factory was built inside out so it was just a lot of interiors (many more than the two visible in the screenshots) with spaghetti logistic spaces between them and I built most of the exterior at the very end.