Much has been said of the fact that movie protagonists fail to wear helmets even when they wear the rest of their armor; this is because helmets would obscure the faces of the actors and thus render them difficult to spot within the action.
To this problem I propose the solution of the Sutton Hoo Helmet, for the helmet is
1. Distinctive
2. Badass and
3. Fully functional
such that creating a set of such helmets, one pattern for each hero in question, would render them distinct on the battlefield in a plausible manner. And I think it a pity that Peter Jackson did not take such an opportunity in The Lord of The Rings because the existence of an Anglo-Saxon style helmet would have been perfectly in keeping with Tolkien's love of all things Saxon.
On the other hand, such a solution creates a scenario where the actors have to emote in the manner of Power Rangers, which is to say, bob their heads a lot to make it obvious they are saying something. This was the problem that faced the actor playing Darth Vader. It is a credit to his acting skills that he wound up looking menacing instead of goofy. Although the outfit definitely helped.
It is also true that actors very much like their faces, because their faces are their brand; while a few actors such as Doug Jones and Andy Serkis have made a career of playing people who look nothing like them, most actors wish to have their face on-screen.
I propose a different solution: Everyone does sci-fi movies where they wear fishbowl space helmets, like in the good old days.