Some technical rules require bodywork to be visible from beneath or not visible from that position.
Tranparent bodyparts should get around some of the rules I think.
To give an example, the teams cut slots through the "boomerang" over the bargeboard fins that are vertical projections of gaps btween said fins. We know these slots can trip the air a little because we see teams tape similar small gaps on the engine cover.
I wonder if the slots could be filled with transparent material to satisfy the visibikity rules, or even the entire peice of bodywork be made of transparent material. There should be some aerobenefits from this.