Inflatable? If it was molded, it would have to be something that you could easily remove and then reinsert into the next shell?

Of course, I have no idea what the actual tech is available right now.

The best solution would be to design a helmet where you can just emplace / remove an ultra lightweight casing that goes on the outside of the helmet. Then the equipment manager only has to change the graphic. You'd have to have a material that would work, even on top of scuffs and scratches, other superficial damage. That could get expensive too though...