I have a friend who started off with goats by keeping two rescue goats in a loose box. He got a lot more into his goats, and had to convert all of the stables into goat pens! He split two looseboxes into 3 pens each. Each pen was smallish, but he split them by building half a hexagon at the front as an entrance, the pen in the middle was smallest and rectangular, and the one at either end had a triangluar edge to make it slightly bigger. What helped the size was that he made head holes in the door, and brackets for their food bowl and water buckets outside the pen door.
Haven't got any pics I'm afraid, but it did work quite well. He built it all himself out of wood.
Beth