"Honduh" and Yamaha as well as others have been making quite reliable engines for quite some time. Maybe you need newer equipment?
My generator was purchased a while back in anticipation of the 2nd ice storm that never came. I run it at most 2 times a year for at most 20 minutes each time. It runs with the same 2+ year old gas that's been in the tank since I bought it. If I remember to flip the switch ot the "on" position before starting it it will start and run just fine on the 1st or 2nd pull. I do make sure to turn off the fuel to the carb and run it until it stalls before putting it away.
My mowers (I'm on my 2nd one) start every time as long as there is gas in the tank. Same for my weed eater. I leave the fuel in the carbs with the lawn equipment.
Modern generators should have the same reliability, if not better, since it will get used nearly once a month so the gas will be always fresh. We would also be a "light" duty user of a generator.
The Yamaha unit I have in mind will provide 1000W of clean power all day long on a single tank of gas. It will be a quiet 57dB at full throttle. If you are quiet, you might hear it over the keys on my keyboard clicking away. Anytime we start the bus we stink up the place, make unneeded noise, and it continually proves to be LESS reliable than my mowers, weed eater and generator. The Yamaha will also shut off automatically if the oil gets low (the bus won't do that).
The generator weighs *less* than a single battery that we currently use, and it takes about 30 seconds to recharge a generator.
http://www.southwestfastener.com/ef1000is.html
As for wiring, there is a minimalist approach. It's called an extension cord and power strip. Use AC for what needs it, and convert all the 12V DC stuff to power bricks and everything plugs right in. NO FUSS IMHO. If we don't want to convert to power bricks, then we can always run the DC stuff off of the 12V DC output of the generator.
Even at a relatively pricey $620 it would likely run flawlessly for a minimum of 2 years, at which time it is *almost* disposable.
As for maintainence, I can change the oil and spark plug in less time it takes to charge the multiple batteries on the bus, AND I would only need to do it once per season rather than the suggested EVERY event battery recharging.
The two LARGE batteries connected to the bus' charging system would be the "redudant" backup.
When the bus bites the dust the generator is portable for it's replacement. Most any upgrades done to the bus will expire when it expires.
Of course, we are still making a big stink about nothing since on page 1, post 2 of this thread we already determined that there are issues with the current wiring and *those* are the real problem.
Scott