Dual generators would use up a lot of space in the storage compartments. I would rather just have a single 20 - 25 KW generator.
4 or 5 rooftop air conditioners are a must have thing to have in a RV that long!
Most of the things in the RV can run from a 8 KW 24 volt inverter/charger. It is normal to have a 24 volt starter motor when the displacement is over 750 cubic inches, and they already have the 150 amp 24 volt alternator on the bus. They would also typically have a 250 amp 12 volt alternator too!
Looks like he had a plan, and this is not his second RV, so everything was planned ahead of time!
Fred.