It sounds basic but you should make sure you think about your work triangle like they do in kitchens to save steps while you work. In the kitchen it's cook top to sink to fridge. I'd say in the sewing studio, it's sewing area to cutting area to ironing area. The smaller this triangle is, the better and more efficient. Also, I'd suggest adjustable tract lighting over the design wall if possible. I have that in the mountain house and it's wonderful. Also, if your windows face any direction except north, you'll want to consider putting a glare reducing film like 3M on them. This will reduce eye strain from all that direct sunlight especially if you have lots of windows. This will also protect fabric as well.