What an awesome idea! This would be great built in a kids walk-in closet! Just take the doors off the closet and utilize the extra space! Keep the kids clothes etc in a wardrobe in front of the closet to make it a secret hideout!
Love this play area over the bed, like the anti-loft bed. I think I& leave off the first couple of steps of the ladder and make it a safer place for the older kids to play with and store their LEGO creations. (Apartment Therapy with loft bed inspiration)
Bunks in the closet, leaves the rest of the room as a play area. This is a GREAT idea! I would take the doors off though. Maybe cute curtains instead. I used to love hanging out in my closet. And to free up the room for more play area?