They tried, but alas they couldn't make a helmet for a head that big and still fit it inside the armour cowl
Maybe they just shielded his bald cranium with subdermal armour, Odalisque-style? It's important to keep your head free when dealing with the Combined Army after all; Morats are frightened by beards larger than their own.
Please remember that due to the printing and subsequent moulding process some features need to be exaggerated in order to account for printing quality and subsequent shrinkage, plus renders are viewed in a far bigger scale than they are intended to be.
You would think his armor is the best defense he have, but no, it is that so perfectly polished forehead that can deflect anything thrown at his face!
Ariadna is the Imperial Guard of Infinity: cheap bodies you can sacrifice and still get the mission done, incredibly tiring to deal with because of the amount of camos they can deploy (and yeah, you can counter that with sensors and sniffers... but they can shoot your sniffer-carriers with their ARO troops anyway, who tend to also be on camo), and with access to weapons that can give a bad day to any enemy. They also are the at the lowest point regarding technology in the factions lists (only Pano's Ateks are worse...), and for the most part deal with technological obstacles with generous amounts of firepower and explosives.
Also when Ariadna field twice as many soldiers as their opponent we should not understand it as they have twice as many ressources. It's more likely that Pano or Yu jing have tens or hundreds times more soldiers than them. But to be on a equal footage on a single operation, they have to dedicated twice as many soldiers to compensate for the lack of high tech gears. That being said they have only one planete to defend and one major foreign operation (paradiso front).
Continent, not planet ;) Ariadna doesn't have manpower nor resources to properly claim the other big continent.
We’ve probably answered the armour question, with Wildfire dropping and O12, it’s almost certainly an O12 modified/upgraded Yu Jing suit. Who knew?!?
Edit: well, what do you know, there's a graphic on page 3 of that thread that I've missed. That looks like the normal hype cycle for a new faction CB likes to do.