A truly outstanding model railway in "limited space" !
A relative once rented a split-level duplex with geothermal heating, and there was a tall crawl space under one half of the living area where someone had left carpet over the gravelled crawl-space floor to use it for storage. It occured to me that it might have been a nice large usable space for a layout, and the geothermal heat piping under the living space floor kept it heated comfortably in winter.
If I ever had occasion to make use of such a space, it might be fun and practical to sit on a battery-powered cart running on its own rails around the layout as a "service railway", as an alternative to crawling around the space.