Just going to crib from my comments in Discord. But I feel like the thread hasn't sufficiently grasped the Gravitas of Malcador basically responding to our letter by saying 'I don't trust you now, but stay in your lane and don't fuck things up'
We are so far past that.
It does feel like Malcador is being like 'see what you've almost done? Now sit in the corner while I fix your mess' to the Primarch LEAST likely historically to stay in his lane. Like what was the point in saying 'maybe come talk where I will say things and hope you listen. But let me remind you for the second time that I think this is pointless (but I'm still trying, it's not like I like you or anything, idiot)'.
Like, I think someone put it best in thread, but he just saw Kesar ready to start a Civil War on accident. If someone sufficiently motivated Kesar, he could end up leading one on purpose, and there are at least a dozen Primarchs with some sort of grievance or issue with the current way of things, and all of the ones who weren't sufficiently feeling rushed before now will feel that need when Emps decides to slap a handful with restrictions (for no real reason, honest!) And they freely mention "Yeah, no, it's because he thinks we're traitors."
If it's to the point where the Primarchs are willing and ready to make a public show to the military that they're not loyal, then why isn't the response trying to reach across and regain that loyalty?
If we meet with Malcador, that's basically it. That's the point of the meeting. Like. How are we going to fix this that isn't just you making a bunch of hurt, angry and now distrustful powerful people too useless to muck up your plans? Because that's not gonna work. You have like a year to get back to us. Not five, not fifteen. I don't think you can delay it any longer than that, and I don't think Kesar could either if he tried.
I can really only see this meeting being trying to drive it home that Malcador can't just bury this. He definitely can't bury a dozen Primarchs like he tried to do to Vulkan, with too much to bear until they just collapse and give up and give in and stop trying to do anything Malc and Emps don't want them to.
Either they actually address the Elephant in the room, or at best that's it. Primarch Domains stop responding to orders from Terra. And that's the BEST case scenario. That's what would happen if Kesar and the more level headed but still angry Primarchs got together and got the ones ready to throw down to deescalate.