I would consider the best side of the house also. But I see you are in Texas. What side of the house does the storms hit? I would pick another side. Also, consider lots of closets, maybe a whole side, but on the inside wall. I would consider a little bit bigger instead of 15'. Draw out 15' in one of your rooms and see how it looks. The 25' is okay.
You need a half bath too, TV cable, phone or WIFI, and lots of light except on the fabric, that is why I said lots of closets. I would get wall to wall closets as deep as your top kitchen cupboards. That is great for fabric. Somewhere else you could put the batting and the larger pieces. Do you see a long arm in your future. Make the room much bigger. Best of luck.