I always thought it would be fun to make a 3/4 or 5/8 scale fullsize Pac/Galaxian style cabinet with a 13-15" monitor in it.
I love that shape, but the size of a full scale cabinet might be too much for a little room, and it would be perfect for littler kids to stand, or adults to sit at. Instead of 66" tall and 24" wide (or whatever), make it more like 50" tall and 18" wide. Much lighter and more portable.
The narrower control panel would limit the number of controls, but for the vertical classics that's not much of an issue. You could easily fit everything one player needs in 18".
It would essentially be a cabaret sized cab shaped like a full sized cab. I've seen Neo-Geo kid scale cabinets that are this way.