I know this suggestion is a little late in coming, but as I was standing in the new area, with the cold but bright sun streaming in the south-facing doorways, I thought that it sure would be nice to have a couple of windows in those doors. They wouldn't have to be fancy, and would provide light inside especially in the winter time. The new extension is a really nice, large, unobstructed space which should be a pleasure to work in. Natural light was a common feature of many factories and workshops in the 19th and early 20th century. The door windows can be added later on when the weather is better, but it might be easier to plan for them now while the doors are being rebuilt.