I assume it has been doen this way to make things easier. Presumably the alternative was to have no helmets at all?

Thanks for the explanation Tumerboy. It would have been nice if EV suits were handled like kits and drawn over your original costume, but I'm sure it was simpler to implement this way.

With that said, I would still like to see transparent faceplates for the STF suits -- the M.A.CO., Honor Guard, and Omega Force Mark XII gear. Those are costume pieces that can be customized at the Tailor, not a full avatar replacement. We already have head replacements like the Bajoran Vedek hood which use the character's face. I should think that a helmet could be made that works the same way.

I always wondered how that would work. For that matter, what do Andorians do with their antennae in those helmets? Must be uncomfortable for them.

I'd have a cosmetic button for that or at least make it an automatic on-off of clear vs. opaque based on "background light". You'd want it on for spacewalks, for example, but not necessarily on a planet. As for ability for the company to easily implement, not sure. There are such helmets in Champtions, but it's a static costume design for a character. Not sure if that fits for this.