I once used this style of helmet as the basis for a Very Large hat. (Sorry, no pictures available.) I pop-riveted a steel wire armature to the helmet, and covered the armature with cloth. This style of helmet fits better than a regular bicycle helmet, so weight and wind is less of a problem.
Do beware of the weight of any large headgear. My hat was so heavy I had to move my head very carefully to manage the inertia. Also, beware of heat inside any headgear on the Playa in daytime.
Now build a cool helmet!