Is it possible to have a button to hide/toggle the HUD?
TL;DRA HUD hide toggle is something they'll take into account while overhauling the UI and Director Cam, along with showing only contextually relevant UI, but no specific commitment is given.
They get a lot of Developers asking about how to do this. Zane says that as they overhaul their UI, they'll be improving the Director Cam system, so it's something they'll take into account at that time, especially since it'd also be helpful for the Devs. He suggests though that it could go further, such as being able to choose what you want to hide, like only the visor HUD, or maybe to hide all of the UI but not what's in the environment that brings it to life - like "background fluff screens". Simon adds that for the general UI, especially the visor HUD for FPS gameplay, they want to have a system which only shows you the UI that's relevant for you at the time, so if you put your weapon away you wouldn't need to see the weapon UI in the corner of your screen, or maybe you wouldn't show Health unless you get injured. This kind of work, which will result in only showing things when they're needed, should also help to de-clutter the screen.