Great idea, I think that you'll find a larger kitchen will be a big benefit over closet space. I'd start by figuring exactly how much space your son needs, with the estimate on how that need may grow in the future. You could take over only as much closet as you need, and supplement it with a free standing wardrobe. If it's not hanging space that he needs under bed storage might suffice. Closets are fairly simple to frame in with 2x4s. Size the opening to your doors: bifold, sliding, hollow core or anything better. You could also use a simple rod with a curtain if that works for you. Can you take over space for a closet from an adjacent room?
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