Was it already in the lore?
It was indeed. I can't give the specifics of its place in the lore beforehand, as while I like the setting of the Mortal Realms, my appreciation is less the fixed points that GeeDubs like to obsess over, and more the concept of the open setting with enough space to create your own slice of it without risking canon conflicts - much the same as 40k has enough planets that you can create your own star system of battles and there is little to say it doesn't exist in some capacity in the canon.
So long as you don't include canonical characters... because seeing Guilliman getting shanked on some no-name planet, while hilarious, is obviously not going to be canon.
So, yah, can't point at the direct references. But Cogforts have been in the lore since at least the previous edition of AoS.
The memes are fair. It is hardly a unique concept, but Warhammer as always been a melting pot of ideas poached from elsewhere. Ideas that are then reforged to suit the Warhammer world. I think the Cogfort is a fine addition to AoS from a model perspective. Ruleswise remains to be seen, whether or not it can avoid the pitfalls of being an "apocalypse-level" centerpiece or not. I'm certainly not one to speak on the nuances of AoS rules.
Very true. Even the Emperor on the Golden Throne was itself a reference to Dune, where the Emperor sat on the Golden Lion Throne. Never mind all the meme regiments of Imperial Guard. Don't try to convince me that the Deathcorp of Krieg aren't specifically meant to be a meme regiment. Cadians were obvious movie-Starship Troopers. Though with Cadians, I think they're sort of trying to move past that origin.
As for whether Sigmar's Moving Castle can avoid those pitfalls? Hmm... Probably not, but I'm saying that from the perspective of somebody who has long since lost faith in GeeDub's ability to write rules. And yet, fool that I am, I hear about "new edition" and I think to myself "will they improve the rules? I must have hope!"
Their announcement of 11th Edition 40k... trying to bridge Narrative and Competitive Balance... like, cool goal? Will be happy for the 40k players if they manage it... but words are cheap, so until I see the result, I have to remind myself that optimism is not my friend.
As much as I am naturally optimistic, I like being a pessimist. Being a pessimist means I either get the satisfaction of knowing I am right, or I get to be PLEASANTLY surprised. XD