Picture this in your mind's eye: a squad of deceased, cybernetically-augmented, remotely-controlled "undead" Loyalist Space Marine bodies, with their armor still painted in their original Chapter's colors (in this particular case, Imperial Fists), but with the Iron Warriors symbol and/or hazard stripes visible on one shoulder guard (representing their subservience to their new masters, the Iron Warriors - a deliberate and calculated insult to the enemy...heh!). All of these "Automatons" have Necron Warrior heads replacing their Space Marine helmets (representing the fact that they are lifeless, robotic automatons).
I plan to add some significant battle damage to their power armor (primarily in the form of various types of bullet & shell holes, blast cratering & scoring, blade-gouging, and so forth) before final painting is done. This will help to convey the idea that these former Imperial Fists have been mortally wounded in honorable battle against their hated enemies, the Iron Warriors - but, after their deaths, their lifeless bodies were collected from the battlefield, subjected to vile, macabre acts of necromancy (both sorcerous and mechanical) by the Iron Warriors Chirumeks (Dark Apothecaries) and corrupted Techmarines, and then forced to serve their vicious murderers, fighting against their former Imperial Fists Battle-Brothers in the Long War against the Imperium for the rest of eternity!
These warriors are already dead, and are therefore Fearless. The mechanical minds in their cybernetic replacement heads possess only rudimentary motive and combat programming, making them Slow and Purposeful. Their dead bodies, now impervious to pain, also have numerous mechanical and structural augmentations, giving them a 4+ Invulnerable Save ("Counts-As" Mark of Tzeentch).
Their limited programming requires that these "Automatons" be maintained and serviced (and remotely controlled) by a corrupted Techmarine ("Counts-As" an Aspiring Sorcerer" - pic coming soon!), who leads the Squad (a la the "The Sorcerer Commands" rule).
The "Automatons" bear specially modified, Ultra-High-Velocity Boltguns (which I will make using Necron Gauss Flayer barrel tips as barrel extensions) that fire specially modified Bolter shells which have sorcerously-enhanced armor-piercing explosive sabot charges. These enhanced munitions, known as "Inferno Bolts", are able to penetrate virtually any existing form of body armor (AP 3).
I was thinking that a fielding a Squad of these Iron Warriors "Automatons", painted up in Imperial Fists Space Marine colors, would be a thematically "fluff-appropriate" way of representing Thousand Sons Rubric Marines within an Iron Warriors Grand Company. It would also be an ironically fitting (albeit perverse) tribute to the ten thousand years of HATE that the Sons of Perturaubo have for the Ancient Enemy! And, on top of that, it would also serve as an appropriate little "knife-in-the-gut" to any deluded Lapdogs of Dorn that one might face on the tabletop...
Painted pics of these "Frankenstein's Monsters" coming soon...
IRON WITHIN! IRON WITHOUT!