A really great project, I like this one! There are some maquette trains available in 1/72 and in 1/35, but those are static models, do not roll like this one.
Has anyone else done a project similar to this one?
I have a mine cart train for 28mm/1/35, made onto a H0 train

Jim Jackaman did and used Lego which is very out of the box thinking!
I know some 40k armoured trains made onto Lego train chassis, I find it a really great idea as Lego trains are durable, come with standardized tracks, customizable chassis and the Lego-y parts are covered by the plasticard superstructure anyways.