The more I think about it the biggest issue i'm seeing is that a lot of people in-universe and out are pushing towards certain ideals because of the merit of them sounding good
on paper while failing to take into account that the reality would be different and deviate from assumptions. For example:
"Do you mean if he could avoid becoming a figurehead?" Kelbor asked directly, "or if he could make the decision to purge entire worlds over memetic hazards."
Kesar opened his mouth to ask how much he knew before Mortarion interrupted him. "There wasn't a point to keep it a secret, he's on our side, hiding this would only drive us apart in a few decades."
"And you just told him? Do you know how illegal that is?"
"I am literally planning a civil war right now."
"Before we get too off-topic," Kelbor interrupted, "if you had kept this information from me, it would have driven a wedge between us. Why the Emperor didn't tell me confuses me, the idea of being a god's slave does not appeal to me."
"It's because just knowing of them gives them power," the Primarch's voice was calm, now back in familiar territory, Kesar found himself far more in control. "And so only a few may know of the Archdaemons."
"And the leader of the group that provides almost all war equipment in the Imperium wasn't informed?" Kelbor asked in surprise,
While the idea to keep any information on Chaos to as little people as possible seems like a good idea on paper in practice it leads to a ton of issues. Main one being that it makes it a lot easier for people to be unknowingly corrupted trying to research them. Something that could have happened to Horus since it's been confirmed that if Kesar didn't meet with him he would have tried to research Chaos on his own.
Then there was Lorgar, and yeah while it was Lorgar him not having any information on Chaos made it extremely easy for him to be corrupted by Chaos agents. Which brings us to the banning of religion thing. While it sounds good on paper it's outright canon that existing religion can actually be extremely helpful against corruption since a person who is already following a religion is less likely to fall for Chaos' lies and rebuff them depending on said religion while also starving the Chaos gods of faith.
In fact it would be a lot more practical to just either support religions whose teaching are counter to Chaos and thus extremely resistant to being messed with by Chaos and/or just modifying religions to be so. We have seen this with the Cult to Kesar which actually gives people CR.
This also gives another example of the Emperor bias blinding him to other solutions. Again to use Lorgar as an example it would have been a lot more practical to just say convince him to join another religion that was outright counter to Chaos along with being peaceful and tolerant. Hell, if Emps was truly practical he could have pointed him to the Mechanicus which honestly could have solved a lot of problems once you think about it. Another point against Emps 'not needing' his humanity.
Something that I think is important to remember here is that Kelbor and Mortarion are definitely not wanting to rebel for the right reasons. Mortarion just wants to spite Emps and Kelbor just wants more power no matter how logical their points are.
Not exactly true, Kelbor does have legit beef with the Emperor and has expressed at the very start that he didn't even believe him to be the Omnissiah. This on top of Emps control freak tendencies, even if Emps does mean well, and forcing people to join the Imperium. Not to say that Kelbor isn't self interested but he does legit want what's best for the Mechinacus as a whole
@Daemon Hunter Since it needs to be reviewed again, just what does the Imperium know about the situation in the BTW?
IIRC Horus himself got a far more better picture recently and just informed Emps with a letter. So think that it's reasonable to believe that Kelbot and the others aren't up to date on the new information on the BTW.
The main factors for that are the mindsets of the two groups involved. At the moment, both factions are extremely aggressive, which leads to massive losses which would allow for a relatively quick victory. If one of the factions changes tactics to a more defensive style of war however, and the other one takes up siegecraft, then it'd take millennia for one side to win.
Something to take into account that it seems like we may need to worry about the rest of Chaos getting involved. Because due to our actions Chaos is not only weakened but getting weaker over time if Kesar and the Wardens along with the rest of the Imperium keep things up. Them getting involved may be a desperation move.
The way I see it despite the risks the rest of Chaos stands to gain from the BTW ending soon. If the Orks win then they will launch an invasion into the Materium which would not only drastically weaken the Imperium but potentially kill off at least some of the Primarchs. If Khorne wins even if he becomes more powerful himself Chaos as a whole gets a giant boost and buffer against the sane forces.