Acid attacks steel just like electro-plating - the material is deposited disproportionate to the surface area. It removes the most material from edges, corners and the ID of holes.
It removes the least from flat surfaces, like all panels.
This is the very worst thing from a structural standpoint, since the weight loss is minimal until the corners and seams fall apart.

The entire panel must also be neutralized (baking soda, dilute lye) after thorough rinsing with water, or the remaining acid will completely destroy the panel. Submerging absolutely won't do it. Even cars carefully washed sometimes don't completely flush out (direct path from the acid to the exterior). For the final rinse, boiling water from a pressure washer is best.

Sandblasting works OK until your operator forgets to angle the nozzle or turn the regulator down, then you have a washboard instead of a hood. The bondo weighs much more than the weight saved.
There is also no such thing as "effectively masking the area" to allow blasting on assembled pieces. It never, ever works, and you can get sand out of it 5 years later.