I'm sorry but these are cars, expensive for sure but still cars. They're made of paint and metal, you drive them. If we're too precious about them the whole point of owning a car is lost.

Drive the thing, enjoy it for what it is.

 

The real issue with gravel roads is the dust. And not the dust you see on the car.

The dust gets everywhere. And it traps moisture. Essentially what happens is you get moisture all over the underside of the car. Above the fuel tank, above the steering rack, beside the engine, caked inside a frame rail, under the seals, inside the chassis drains, etc.

It can be okay if the dust is dry, the car is dry, and the car stays in a humidity-controlled area. If the car is on the gravel road when it's muddy, and/or the car is driven regularly in the rain and the dust, the underside should be inspected yearly, and washed as needed. However, constantly washing the underside of the car is not good either.

Dust and moisture isn't as bad as salt and moisture, but it still can create issues.

The best solution is to fully clean the underside of the car, let it dry, then apply a rust-mitigating wax type material. The factory puts on some (Cosmoline), but it is generally design to really only last for the export boat ride (salt air) and a few years later.