If you do want the lower-jaw protection, try one of these (Ruroc helmet):
1.) They're actually designed for snow sports and are much more low-profile, so it will hardly affect your performance.
2.) The lower section is removable, so you can easily turn it into a "normal" looking snowboard helmet.
3.) The goggles do not fog up.
4.) Get it in the right color, and you'd actually look like a bad-ass!