There is a head accessory slot, it's just empty. You can see it clearly in the last screenshot, the one with the Gunner loadout, under Appearance it says "No Head Accessory". So there should be helmets etc.
On another note, what's up with the new pulse rifle? I kinda dig the visual design but functionally that rifle looks like a real mess.
It looks like it should still fire the 10mm explosive-tip caseless ammo from the top barrel and it's Tommy gun action like the classic M41A Pulse rifle, but the underbarrel part looks like it now houses a second rifle barrel with an AR15 style bolt and brass deflector (therefore, this one is using cased ammo) and what looks like a flash hider / compensator at the muzzle. What the hell? Does this thing use two different actions, two different barrels and two different calibers just to fire bullets out of both of them? It just makes no sense, and therefore makes an otherwise visually decent looking design off-putting.
Judging by the looks, this game went from creative while at the same time fairly realistic and well-researched sci-fi firearms and equipment of the second film to haphazardly and/or ignorantly slapped together toys just because... "looks cool"?
Disappointing.
What's worse, the more I look into this game, the more of these little red flags keep popping up and a very uneasy yet familiar feeling starts creeping in...