I always check in on the 'indoor layouts' topics but this one got me really intrigued. A six foot turntable? Wow! I have a 35x40 foot indoor layout and I don't have room for a 6 foot turntable - or an engine that needs to ride on it.
Is that a typo? I expect that the 6 foot includes the turntable, roundhouse and a fan of tracks.
Still, it would have to go in the middle of the room so you can gain easy access from all sides. Track would have to go around the outside walls on a narrow shelf making the engine facility in the center the real show piece of the layout. An authentic, highly detailed display like that could work.