I don't know what would work for you, but my sewing room sits over the two-car garage. It holds my longarm, one sewing machine, a big cutting table, and tons of fabric. I can function in it very nicely, yet I wish it were bigger. When I was moving and looking for a house, I had to pass up a number of homes because they didn't have a space for the longarm. I wound up with a home that was bigger than I needed, only because the smaller homes didn't have a separate room large enough for the longarm. I envy your ability to design and build your own home with the sewing room of your dreams.