Heli pilots have HUD fixed to their helmet even in case they do not have any helmet.
Also gunners should have PIP gunner view similar to drone video stream so they can look around in normal vision mode "though their own eyes" while having a small aiming window in a corner where they can enable thermal optics, zoom etc.
that's actually an interesting idea, force the hud to be locked forward if the pilot doesn't have a helicopter pilot/gunner helmet.
Or, even better, don't give them a HUD at all, since the helicopter doesn't actually have a physical HUD device like a jet does.
"since the helicopter doesn't actually have a physical HUD device like a jet does.
Are you sure about about that? Then how does a pilot fire unguided rockets?
they have an HMD (Head Mounted Display). In real life, the HMD is not just a fixed screen of info like it is in Arma. For instance, in the orca, when you turn your head the gun reticle should stay in place (otherwise the gun is automatically useless). It would be the same for the unguided Rockets