doesn't the combine already have integrated masks?

If possible, the only criticism I'd have with the head model is to make it integrated with the helmet rather than as a separate mask.

There's a lot of implied gruesomeness in Half-Life Alyx that the Combine Soldier's mask lenses actually REPLACE THEIR EYES, as circuitry can be seen coming out of a Combine Grunt's eye sockets in one of the damaged head models. If that's the case, why secure what is essentially their face in place with gas mask straps?

the smaller, more forward eyes on the standard Overwatch Soldier by comparison make them look more predatory and focused, the Overwatch sends them out to hunt malignant bodies. the Nova Prospekt Guards are meant to defend, not attack.

they probably do now, considering how tiny the eye ports are on the regular soldiers, not mentioning the elites

On a less thematic sense, the larger eyes also would make them seem ever watchful, like Cameras. I wouldn't be surprised if they had a wider field of view than normal soldiers.

damn

I think this strangely fits the Nova Prospekt Soldiers in a thematic sense.

The mask looks more pushed out than usual, resulting on the eyes being somewhat onthe sides, making the Guards look like prey animals...

Sort of because by this point in the story, Gordon has acquired control of an Antlion Horde and is commanding it to barge through the base like a predator closing in on its kill.

The Nova Prospekt Guards are trapped in a base that's being turned against them by the second by Gordon's herd, and now they're on the defensive, with the Antlions & Gordon taking swaths of them out.

It's strangely fitting then that this makes them look like the Prey, because they are.