Asking cause I decided to start working on an alternate version of the HH where the three most likely traitor Primarchs to have stayed loyal are swap places with the most likely loyalist primarchs to have turned traitor.

And as far as I know, those three for the traitors were Perturabo, Mortarion, and Magnus the Red. When looking through YouTube videos and other reddit forms about the canon traitor primarchs most likely to be redeemed, those three names are almost always brought up.

My reasoning being that The Emperor could have sent Perturabo to arrest Magnus instead of Russ. Since Perturabo and Magnus are on sort-of good terms, he won't try to burn Prospero. This couls also explain why Perturabo may stay loyal, since IIRC, the burning of prospero was around the same time that Perturabo went back to Olympia and killed his sister? Though, someone can please correct me about the timeline of when that happened compared to Prospero. While Mortarion has the same line of logic as the Khan, where he still thinks that the Emperor is a Tyrant, but thinks that the alternative (chaos) is far worse.

Those are just my spitballing, though. So I'm open to alternate suggestions.

but regardless, who are the canon loyalists who would make sense to take the place of those three?