This one has always baffled me. The current mapping of the helmet makes it very difficult to create even a simple wrap-around design (eg. a line) without a lot of trial and error, rotating, and resizing. Most racing sims I know of map the helmet by having the lower 75% of the helmet as a long rectangle (enabling seamless wrap-around designs with ease), and a square to map the top of the helmet (although it is traditionally a circle within this square that is mapped). Personally I think this is more important than updating the shape itself as many have requested but maybe this could go hand in hand with it.

As far as I know, an updated driver & helmet model is in the works - but the stage when they're due is unknown (maybe never?). Helmet model was tweaked a bit when BF1 was released, the visor strip was added. Because of that I don't see any updates coming in near future, would make all the "new" designs obsolete.