Originally Posted by
ThePov
Well, as amazing and well thought out that line of logic is (which it is, really. Bravo.), and as much as it explains everything, it does depend rather heavily on one central assumption that is by no means set in stone, only implied in very round-about means, that being that the Emperor is an Old One. It's possible, it's epic, and it would explain a lot, which is precisely why GW won't use it. It's not in the interests of the company to essentially close the book on the 40K story like that, because they can instead just keep making money by giving us one teaser after another (and I'm not complaining, I personally fin the whole process very fun.).
So yeah, you have a very well developed theory that is entirely plausible, but will likely never be confirmed for the simple reason that GW likes to suck as much money out of your wallet as possible.