4 6-cell banks are going to have the ability to absorb several hundred amperes of controlled charge rate. BFL's chart is reality. So is listening to and babysitting a generator for hour after hour. I would be skittish about generator noise and neighbors.
I would choose a 3,000 watt Honda because of the low noise factor. Purchase a 100 amp -minimum- size charger. If that ends up satisfying you, great. If it charges too slow for your taste purchase a 2nd one.
Other than 12 volt battery banks are great for use with inverters and solar homes but an RV requires 12 volts - a lot of it.
The inevitable question: Why so many batteries?
