From the exterior, this looks like a nicely done conversion. White is good for a warm climate. I take it the rooftop structure is a water catchment, perhaps draining to a tank. If this structure were a bit higher, a water storage bag could be placed under it. The bag would thus be shaded, and it could gravity feed to usage points in the dwelling.
It would be interesting to see the interior plans. Bunks, RV-type toilet/shower, cooking facilities, etc. I have seen similar "conexes" made into quite livable shipboard staterooms.
You mention 1:500. Is this in production? With regard to the situation in Haiti, an efficient supply train would be needed. Some pastel colors would lend variety and still be reasonably reflective. Or hire some railcar graffitti artists as exterior decorators!
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In vino veritas; in cervisia carmen; in aqua E. coli.