I'd have to Strictly warn against nids though, D&D already has the like of Kythons, and Kaorti if you want nasty terraforming ayy lmaos and Elder Evil on the plate.
Men of Iron aren't really much, they were A.I machines that went rouge because of mistreatment and because Tzeentch made a Greater Daemon out of a human to A.I and possibly corrupted them easily as they had no souls of their own.
The CSM's would essentially, port in, get stuck, and decide on getting a hold of barbarian tribesmen to turn into effectively make into Warhammer Fantasy esque Warriors of Chaos to work their will as the CSM Sorcerors try to sift through weave-rules which are screwing them over, highly prizign Daemonculaba to promote native converts to the cause, as well as using slavery and fervent worship.
The Local D&D Strain would include four Sorcerers, 1 Word bearer who is able to profess the faith, in spite of contradictions and common Deific Miracles held in the realm, receiving what little guidance it can get via Suel-Katesh, and most certainly a Plague-bearer out to subvert Zuggtymoy followers and Druidic circles to Nurgle.
Despite starting out, they've the benefit of their advanced gear giving them by D&D standards high protection, but their abilities have been nerfed, the Sorcerors unreliable due to Wild magic and spells per day, and at best, the main benefits gained from the venture is heir Word bearer, whom has access to the Madness Domain, next to the Plaguebearer whose work on the druid side of things has gained some perverted version of Thrall of Zuggtmoy class features and access to the Pestilence or plague domains, I think one literally lets you avoid negatives of disease whilst still being a carrier, so it's effectively Nurgle the Power.
Plague, Pestilence Famine, Death, Domains, It's got one of the powers of these and access to some of the spells.
They don't have perils of the Warp but Wild magic Tables, and are bolstered by converted Barbarian tribes.