Looking at first glance, many of the new helmets could benefit from stats revise, current ones are somewhat unadjusted.
Simple Skutatos Helmet need to offer less protection then Roman Helmet, and Roman Helmet more then Skutatos helmet, swaping the values for start would be ok.
Pronoia Helmet design and reinforcement ridge are made to offer better, but let's say the same protection level as current open faced Byzantion Helmet.
Same counts for Clibanarius helmet who should at least be in rank (or better) then Novgorod helm.
On the other hand gotta add that Varangopoulos helmet seems very nicely balanced stat vise, since it's the only open faced helmet with additional neckguard added ingame.
When it comes to armors they also need some love because of their construction. Byzantine equipment in general did not show much of what's under it.
My thougts would be;
Palace Guard armor, it's construction is long padded coat, long mail coat of best quality, padded legs, surcoat. At least to put it just below rank of Mail with Surcoat when it comes to body armor and same protection for legs as Mail with Surcoat.
Archons Armor on the other hand would be of the best quality, since it's intended for nobles and officiers. Putting it in rank with Heavy Kuyak at least, would seem allright.
When it comes to specific stats numbers I'd say Ujin did a real fine job, so getting the values at least close around his suggestion would be a fair deal.