Watching the test footage I realized, the costume was designed to hide the actor's face
because they hadn't picked one yet. Once they do they will probably redesign it for facetime.
Facetime:
They always seem to try to give the actor some facetime. I don't mean that the actors always demand it.
Maybe some do, maybe some don't. But in Spider-Man they said they always wanted to bring it back to Peter.
Make sure the audience was connected to him or something, so he would loose his mask, remove it, etc.
Thor lost his helmet (with the wings) in Thor 1 and has yet to get it back in Avengers or from what I have seen of Thor 2.
For Stark they worked out that while in the suit we can see his face under his helmet. Its a really nice way to
show his face without always having Stark remove his helmet (although he did at the end of Iron Man 1).
In Avengers 1, and Captain America 1, Captain America lost or removed his helmet.
Hawkeye never has a mask like he did in the comics and Black Widow never even had one in the comics.
I just mean I wont be surprised if the Ant Man helmet is designed for seeing more of the actors face.