I started by looking at the traditional origami kabuto to see if there was anything there I could work with. It's a decent representation of a samurai helmet but it very noticeably lacks the side guards (fukigaeshi) and the segmented neck guard (shikoro). I decided to try blintzing the traditional model to see if that would yield the missing parts...
I add fairly generic molecules into the blintzed areas to test whether I'll be able to make the desired parts. Note that the crease pattern for the traditional kabuto doesn't change to accommodate these new molecules (with the exception of one omitted mountain fold at the bottom). It turns out I have more than enough paper to work with so I proceed with shaping these generic flaps into something more specific...
I slightly shorten and flip up the flaps that form the fukigaeshi and flip out some unused paper and add a pleat to make a more accurate shikoro. For the purposes of this demonstration on how I go about designing, I've left the folds of the traditional kabuto model intact...
My first variation on the samurai helmet I designed for this challenge, meant to demonstrate its origins as an update of the traditional origami kabuto. This simple variation can be elaborated upon to change it into the previous version (more pleats in the segmented neck guard, narrowed side guards and more three-dimensional shaping all over) or a version of your own devising.
