That's kinda what I want to do with my house someday... when I can afford to build it. I want a cat room on the main floor with a huge picture window for critter-watching. And I want to build it around an enclosed green area, most likely open air... with cat doors so they can have outside time there whenever they want and they'll be safe.
It's cool to see someone design a house with cats in mind... gives me some ideas!