Very cool.
Wouldn't the shoulder area interfere with the cowl, though? It seems as though you've both sculpted the armor pad that wraps over the trapezius in the reference images.
That aside, maybe you could look into using liquid latex for the mouth make up, like those
venom costumes(NSFW). Maybe even a thin latex prosthetic to glue down around the mouth before donning the cowl. The surface would match the color and sheen of the cowl material more readily than regular facepaint or makeup. Here's another example with latex on the torso of this costumer:
https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-ash2/550067_10100110071208349_1692844116_n.jpg