Most vans on truck chassis will have two alternators as the chassis runs at 24v and the habitation side runs 12v, some other vans with big battery banks or inverter driven habitation air con for use while travelling just make do with one bigger alternator and a booster to make it work hard and I guess get around smart alternator problems.
Some manufacturers are now fitting compressor fridges and only one leisure battery. My van as the same so I fitted extra battery and 200 watt of solar I also need power for my CPAP machine and humidifier.
Big output alternators are used no stop - start vehicles and those with regenerative braking. Certainly on current VW T6 and New Crafter and I suspect that Mercedes Sprinter and probably PSA Peugeot Citroën and Fiat variants are similar.
Ok I can see how a larger output Alternator is useful for mohos, maybe even two, one for cab batts, one for leisure batts, but at what cost in terms of engine drag and fuel economy?, and hopefully even with two alternators they will be the "Smart" variety that know when there is no charging current demand, but even ordinary ones know that AFIA, wish I knew what was smart about alternators on a moho with no stop start etc.
I am still trying to find that elusive Fiat DRS switch,for the rear wing/spoiler, I know its there somewhere as the sales rep at The NEC told me so.