phsycle
Adventurer
Of course they add to the physical payload capacity. Safety sally's love to scream that they don't, but they absolutely do. It's kinda strange, jump on a tacoma forum and people have 3000lb hardside truck campers in the bed, but jump on a different forum and people say you can't put a four wheel camper in a half ton.
What airbags don't do, however, is increase the LEGAL payload capacity of a vehicle. If you roll the thing on the highway with a 4000lb truck camper in a truck with 2800lb's of payload, airbags or not, insurance will take you to task. As will the lawsuits of anyone you kill. 100% add airbags, but use them within reason. I like them as my truck no longer has the factory rake, so with 1200lb's in the bed the airbags prevent squat. As they do when I have a 10,000lb trailer behind me.
GVWR, which the payload is the derivative of, is not simply beefing up the suspension components. Many other factors come into play when a manufacturer determines the GVWR. Chassis, suspension, braking, etc.
Airbags certainly help carry a load but does not increase payload. Even if one were to somehow go through a re-cert process, GVWR would remain the same unless there were some other major changes to the components listed above.