One difficulty with these types of figures with bendable joints, is that they are sometimes out of proportion, with long legs and arms. Also being hard plastic, they won't 'sit' like a real person.
A big advantage of the low seat in wagon, is that centre of gravity is lowered. Not so much of a problem with lightweight figures, but even resin figures(and there are some very nice ones in 1/12th scale) are heavy, and can overbalance small gauged models. The same can happen in real miniature trains, and where as derailing a model is a nuisance, it is far more serious when real people are involved.
Making models that can be adapted for various scales is a good idea, not only saving money and time, but also showing how versatile these designs are as models.
Narrow gauge Francophile interested in 1m, 60cm,50cm , 40cm and smaller gauges . Build in scales from 1/6th to 1/24th. Also 1/32nd and 1/35th using 16.5mm track to represent 50cm and 60cm gauges. http://www.rue-d-etropal.com