So I'm writing a book myself, and I started thinking on things we see in sci-fi and how, for a lack of a better word, silly, some design choices can be if thought about IRL. Like with helmet designs. I think that helmets with visors like Halo's ODST or Spartan armors, or even tiny glass eye slits like with Mass Effect's helmets are huge risks for soldiers. ESPECIALLY if they don't have personal shields like ODSTs.

We're already designing planes without windows that instead projects the outside on the surfaces of inside the plane (but if they do what I see in some of the pics and project it on the floors too, I'll loose my shit), so do you think it'd be a better idea if we did the same with helmets? Discuss if you agree or present flaws you can think of to a design like this please.

You'd want a visor you could open even if it was normally kept closed and sealed, just in case the thing stopped working. Cameras and screens are pretty fragile as battlefield equipment goes.

7383700
Reliability of the technology becomes an important factor; a display-based helmet does run into the issue of becoming completely opaque if there's a severe technical fault.

Cost is also a consideration. A visor is pretty simple and inexpensive solution.

One would have to weigh the costs of the technology against how much it would actually increase the protection of the user. Would that extra bit of armor covering a relatively small surface significantly increase the wearer's survivability?

the primary problem with helmets and armor in general is the heat generated from physical exertion. so when you enclose a helmet you have to have some sort of environmental control like a space suit also a see through face plate requires no power also you can not make infantry invulnerable the three things to remember are mobility, protection, power requirements. You can't have all three you have to balance them current Body armor will stop "most " small arms but will not stop an anti tank round and if you made it to do that then it would be to heavy to move or the power required to move it would be to great

Yeah, it depends on what the visor or slits are for. You'd obviously need a way to see out of the things, and at the times the visors have a double purpose, like a tactical display or allowing visual coms, etc.

7383700
HUD and AR tech is fine, but never full VR unless you where fighting the effing gorgon. You need to be able to use your eyes and ears when the tech fails. If the heat's too much for a well armoured faceplate to take a hit, then you shouldn't have infantry on the ground in the first place.

It depends entirely on how advanced and reliable your tech base is.
If it can be relatively easily disrupted or made inoperable, then a visor is a necessary backup.
But if your technology has some kind of safeguards to offset this liability, then visors are not necessary.
A few examples are the Tau from 40K and Panoceania from Infinity verse.
Tau tech allows them to depends entirely on their sensor technology without requiring a visor, as their helmets clearly cannot open to allow for a visor.
PanOceania are a bunch of technophiles, who love technology. The "eye sockets" on their helmets are a mixture of cameras and advanced sensors that are directly connected to cyborg eyes, so they are more for redundancy than vision.
The point is reliability, if you cannot be reliable then yes a visor is necessary.