I love the scifi soldier image that cannot be denied while portraying class and history. Uniform almost reminds me of some very Judge Dredd imagery. Getting an almost "Honor Guard" vibe. Really digging it.
The uniform the soldiers are wearing remind me of the 18th and 19th Century general uniforms. With that in mind, the helmets look ill-matched with the uniform because of its reminiscence to a 21st Century military helmet.
I understand that the goal of this piece is to generate a sci-fi futuristic soldier under a visionary imperial universe, but the helmet misdirects that because of how modern it is. It's too relatable: it's something we've seen through many soldiers in games like CoD, Halo, and Ghost Recon, where they emulate a futuristic 21st Century military soldier (not a 18th Century regal soldier).
You should follow a similar method for these soldiers like you did for your "Inquisitor" design: less blocky and angular, and retain a more smooth outline.
And cover the mouth. That's one large aspect that hinted at the 21st Century aesthetic.
Good work with these uniform design, but pointer for future reference with military uniforms, all military forces prefer function over fashion. I would reframe from making any uniform flashy if it's gonna be seen on the battle field, otherwise you make them flashy. And I notice a distinct lack of body armor except the helmets. Give your foot soldiers some protection. Other than that, good work.
No problem, but one last thing. Even if they are enforcement officers patrolling conquered territory, the might still want some better body armor protection for if and when they run into ambushes set by partisans and resistance fighters.
It might use a future material that's more flexible. (Carbon fibers? Spider silk?) Or they could use many small patches of armor on a flexible backing, like scale mail.
Or they could just wear armor under the coats. The fact that the armor isn't visible might give them the element of surprise and make them seem tougher, almost superhuman, when an enemy attacks what they think is an unarmored soldier, but then the soldier shrugs it off. Don't underestimate the psychological edge that could give.
Or it could be that the armor is vulnerable to rain, cold, sand, dust, bright sunlight or something else, and the coat protects the armor.
Or maybe they care enough about PR to wear stylish coats over their less fashionable armor.
Or maybe armor offers no protection against their enemies' usual weapons, and would only drag them down.
But all of these explanations are really just excuses for the fact that long coats look awesome.