This might not be a whiff in the real world, converting railway coaches/carriages into holiday homes as someone down in Cornwall started something similar when they bought a disused station and found it had a siding with a four wheeled , six door with 18 windows coach in disrepair. They converted the coach into a spare bedroom and went about buying carriages to restore, to use as holiday homes. Their best find is a carriage used by Queen Victoria.
I was brought up playing with 00 or ho gauge but I think something like O gauge (1:48 scale) or G gauge (1:22) although sometimes sold in 1:24 scale would be easier as they are closer to the Dolls House interiors which means I can adapt the furniture and fittings.
As a sideline I would love to create my own version of a military train , either static or from rolling stock. There's several kits available based on real world military trains although using 1/72 or 1/76 scale with 00gauge might pose a few problems .
I'm sure that I can adapt a 'toy military train ' into something more sinister or from the Cold War.