Helmets are ok specially taking in count that we explore diferent worlds with diferent atmospheres. But on a game like this, character customization is very important to feel diferent from other players. So, if we will not be able to watch the faces of the characters on missions due to the helmets, how about adding masks too, or even helmets with a transparent glass like front? There was a couple on Halo, that allowing to see through them, were great to see chars face. Plus, in planets with breathable atmosphere, would be great having the chance of unwearing the helmet.