To me the Blood Angels Codex pretty much sets it up as the last suviving member of the Sanguinary Guard Azkaellon is Sanguinor, certainly an idea I'd buy into more than the idea that the gems on some Primarchs armour are actually Eldar-esque Waystones.
The Emperor was blinded to the shifting paths of the future, the Chaos Gods may not have been able to manifest in real space but they could certainly block the Emperor's foresight.
Other than Magnus and Alpharius/Omegon who amongst the Imperials knew of Horus' corruption before it was revealed at Istvaan III?
who said he was definatly blinded to the shifting patterns of the future when he seems to know that mankind is on a very narrow path to extinction. i think he would probably be more blinded to the fact that horus would betray him of all primarchs than any other thing. maybe he knew some would turn and hazard a guess as to which ones seeing as he was quite cold towards some primarch and quite fatherly to some.
i was under the impression curze knew what was gonna happen and when he was having some fit the emperor was able to sooth his pain so i cant see why the emperor wouldnt be able to read curze's thought and gain knowledge of what was to come.
plus there was that girl in 'the voice' who tried to send a message from the future of things yet to pass but that sister killed her and how it was written see seemed to have a idea of what the meaning of the message was.
now as to the actions of the sanguinor in bloodline by also stopping a message being sent back from the future we have another instant were yet more imperials are trying to get word to the emperor and are yet again stopped by a imperial.
now for me why is it that this message ,time and again, is being prevented from going through to the emperor and by loyal forces at that. and also when magnus and the emperor commune with each other when he breaks through the webway gate surely the emperor would be able to gleen the deeds of horus from him too.
for me there is too many instances when the emperor could be informed and he is not and it gets me thinking he has a plan that has a slim chance of working to combat chaos and needs things to run his way. yes there will be sacrifices but they are worth it in the bigger picture.
but if he has seeded certain ways for him to have his generals for the final battle then their sacrifice would not be in vain.
hell a wraithlord type body for the most noble of all primarchs and a necrodermis head for ferrus and you got those players back in the game.