www.britmodeller.com/forums/index...

Re-reading this, some of the Scion Beret and moustache heads feel very in line with the SAS/RM Commandos during the Falklands War vibe I get from your concept document.

I think your best bet for being able to find models and recognisable is the US AR type platforms.
The UK used the SLR and then the SA80 (the bullpup design in 3rd image).
Again for modelling purposes any sort of AT-4 type system will look recognisable enough as long as its not an RPG type weapon.

It is raised from the dirt, even as the previous bearer's remains are crushed underfoot.

Cowering amongs the dirt and blood, a flurry of wretched forms scramble to react to the barked orders. A small green hand clutches a battered pole, topped by a ragged and ripped strip of material, hardly enough for a flag.

Shrugging the pain of the wound away in moments before glancing around for his attendant Makari.
"*OI, GIT UP YA SQUISHEE!! FIND ME ANOFFA TRUKK, THIS ONE'S BUSTED!"*

The creature's massive Klaw crunches down onto the wounded Eremiel, ending another proud son of Sanguinious with little effort.
Ghazghkull turns and rips out a fizzing powersword from where it is stuck in the meat of his shoulder.

The Ork bellows, albeit there doesn't seem to be any difference when the monstrosity speaks again, almost respectfully.

*"BUT YA KRUMPED ME BOYS UP REAL GOOD, NICE UN!"*

However when his helmet is ripped free and the words Eremiel is gasping become clear, the Ork Warlord pauses with confusion.

*"I ENT UR 'ORIS, YA STUPID BEAKIE!!"*

Living his gene-father's own brutal demise against the Arch-Traitor, battered and broken, tossed to the ground over and over and still rising, spitting blood from his fanged grin, he staggers forward before the enormous Ork, almost double in height and certainly missing several times over.

Once-captain, now just Lost Brother, Eremiel screams his fathers name, flesh burning and gene-hanced blood leaking from a dozen holes punched through his gold and ash blackened plate.

++Father! No! Let me face him! Horus!!++

From a nearby ruin, heavy bolter fire splashes across the oncoming horde but it is not enough to relieve them, nor is it enough to distract the brutes tearing apart his flock.

Lemartes' squad are marroned, pressed back by the massive weight of Mega-Armoured bodies and overcharged melee weapons pressing them further from their brethren on foot.

Chainswords and massive Choppas rip through armoured bodies alike and the stench of chemically enhanced blood and spores hangs heavy in the air.

Separated by the now wrecked Battlewagon, so close, mere meters apart and yet too far to mutually support each other.

The Orks around are still chanting, this entire group of them seemingly enhanced in size and strength by the sheer presence of their so called figurehead.
Powered klaws rip through astartesian ceremite as powered weapons pulverise Orkiod flesh.