It would be interesting to see the specs on the offering. A "worksite generator" could be 1.5 to 2.4 KW, easy to support with a 200 amp alternator matched to a good 120V inverter of that size. Most current offerings of "emergency vehicle" or "ambulance" packages for Class 3 to Class 5 trucks readily handle these loads, so what might be novel is moving the option (easily achieved with an alternator upgrade) down into the Class 1 truck market. Hybrid tech not needed, just install a bigger alternator at a cost of about $30 at factory.
The loads you are speculating about for RV needs are in the 8-10 KW range, requiring up to 40-50 KWH battery storage for your scenario, and 800-1000 amps of alternator capacity to back it up. With respect to engine output, 10 KW is in the 12-15 horsepower range, readily available at a fraction above idle for any prime mover capable of moving a 7 to 20 ton RV at highway speeds. It is just a matter of supplying a large enough generator or alternator was attached to the engine. Hybrid tech usually means installing an alternator/motor in the 20-50 HP range, so with a hybrid the electric powerplant becomes a freebie rather than an extra cost option.
There exists, today, "all electric" Class A and Class B motorhomes with such capabilities, without any need for hybrid propulsion. It is just a matter of sizing the battery bank and the engine-driven charging system. The Class A offerings usually have an independent genset backing up the batteries, as the smaller 10-20 HP genset
engine is usually more fuel efficient than running a 400-600 HP prime mover at idle power.
