If you wanted a double decker that would be a crore (Volvo and Scania double deckers).
Your best bet is to get a reliable Hyundai Universe assembled by HNS motors locally (body only without any interior like seats etc.). Then customize the interior using standard RV cabinets, kitchen hobs, shower systems, Bed systems, Potable, gray and black water systems, 12V electrical systems etc.
Indiana in the US is the headquarters for RV manufacture. While Italian RV's are even better. I don't know who supplies Italian RV stuff in Italy, do some googling.
BD Army has standardized on the Hyundai Universe, so that means parts supply locally is well assured. Not as good as HINO (Aftab Motors) but pretty good.
Bus Transport companies have started adopting them in the last two years....