Some of the WFCO inverters have a pass-thru feature, but I have never seen it connected. The 120VAC plug attached to these units is always bundled and taped.
This scenario then allows for the unit to only produce 120VAC from your batteries and sent into the outlets marked with a blue sticker that says 'Inverter'. If it had a pass-thru feature, you wouldn't need redundant circuitry and separate 'inverter-only' outlets which are NOT energized unless you have the inverter on. They are NOT energized by shore power or generator.
This is why they always appear next to a regular 120VAC outlet.
Airstream should step up and do 2 very important things:
• use a quality
inverter/charger like a Magnum (they ARE used in their Interstate coaches) that will also serve as a great, fully programmable battery charger
• enable the pass-thru feature on a unit like a Magnum so that they don't require duplicate outlets and circuitry.
The number of outlets and their load capacity will be limited by the size of the inverter, but they would be marked so thou know which ones would be energized from the inverter. The pass-thru feature would also energize these same outlets on grid. Larger inverters can power every outlet in the trailer
This is how I wire my inverters, and I install between 25-35 a year.