A great design. If you don’t use it in high speed motorways, you don’t have to worry about vehicle being too tall. I understand you people are going for the look to impress. But in warmer countries like yours, there is less need for excessive insulation. Try making the similar design with a pop up roof. Be a lot lighter and gives much better mileage due to better aerodynamics. Again impressive design, but placing toilet at the back will give you unexpected surprises due to multiplied effect of going over bumps if you can imagine.