​Vertically mounted model train sets

Ive always wanted a model train layout but I live in the city and the main issue is space.

I thought it would be interesting to develop a model train set that can be mounted vertically to a wall. Very small scale, the size if a large poster.

It would be a complete kit with landscape, trees, buildings, track, locomotives, cars. Like a nice lush tabletop setup but vertical. It could of course be added to and use an existing small scale like Z.

The main thing would be developing a method of keeping it vertical on the track and still running. I figured maybe magnets would work. Or some sort of wire like how streetcars function.

Think its technically possible, and sellable? It would be a high end product for enthusiasts that live in cities or small spaces.