Welcome to heresy!
Nice idea so let me throw down my 2 cents.
In my mind the Blood Angels would be the Khorne worshipers but if you want it to be the space wolves then I'd say the most likely god for them to follow would be Slaanesh. So if you're looking to keep the Wolves Khorneate then your Slaanesh worshippers would probably by the Sons of Sanguinius.
Flesh Tearers: Post-heresy assuming Sanguinius plays the same role as Angry-Ron and survives
Next up Tzeentch, I believe the next most likely to fall to Tzeentch would probably be the Khans Scars due to his approval of psychic powers but that is only a slim margin above the others. I do think though that the best story would be the Iron Hands falling to Tzeentch in a story similar to Mortarion and the Death Guard, they would follow Dorn into heresy but not originally to Chaos worship but over time the discipline and unchanging ways of the legion which rely on the clockwork preciseness, predictable and unchanging way of the machine would be slowly eroded as the war goes on, doubt seeps into the legion command structure all the way up to the Gorgon himself until in some climactic battle with a master of strategy, Guilliman for example, Ferrus Manus sees his legion being torn apart as they are anticipated and every move is countered before it has even begun until finally he cracks and accepts that he was wrong. The flesh is weak but the machine is unthinking, unfeeling and unimaginative, accepting this Ferrus opens himself to the changer of ways until he and his legion who once stood as paragons of order and discipline become living embodiment of change and chaos.
Iron Hands: Pre-heresy
The Hands of Change: Post-Heresy
Slaanesh is a difficult one but I think I'd have to go with Guillimans Ultramarines as they do have a very high opinion of themselves even compared to other legions, we also know that Guilliman is very arrogant (see Imperium Secundus and the Codex Astartes) which I believe could be exploited and built upon until he loved himself so much that he begins to see that the rules do not apply to him and his sons, restrictions are for lesser legions not the great Warriors of Ultramar and so he would begin to become ever more brutal with his methods believing that civilian casualties were of no concern and that they should merely be grateful of his Warriors attention. After joining the heresy he would crusade around the galaxy as Dorns favored general with his conquests becoming more and more debased until the mere mention of his name is enough to cause even the most staunch Astartes commander to flinch. By the time they return to Ultramar the Sons of Guilliman are unrecognizable as the noble warriors who left to conquer the galaxy, though they still stand in tight disciplined ranks and operate with the utmost precision their goals are far darker with civilian populations massacred in the most brutally efficient ways possible always in the pursuit of finding the perfect execution of their campaign.
When they return however they find that the 500 worlds have raised arms in the name of the Emperor and stand ready to defend against those whom they once called Lord and Protector. Enraged, Guilliman led a campaign that lasts 501 days with each day a planet fell to his peerless leadership until finally his campaign culminated with the Battle for Macragge where the still loyal elements of the once glorious 13th Legion make their stand under the inspired leadership of Remus Ventanus who rallies the remaining forces of the shattered legion to exact such a heavy toll upon the heretics that alone among the 500 worlds Macragge lasts for not one but two days of apocalyptic combat until eventually the battle is ended when Guilliman himself descends to the planet and leads the final charge upon the defending forces. Faced with the primarchs wrath not even Ventanus could stand as he is smashed aside signalling the end for what was once the jewel of the Imperium. Ventanus himself is captured and taken by Guilliman to be subjected to horrific tortures until his very soul is flayed, with this last act of corruption Guilliman ascends to become a Daemon Primarch of Slaanesh.
The Apex Legion: Post-Heresy
Nurgle is easier I think as I think the Salamanders already have a lot of his signiture traits, care for those under their protection, have resistance to things that would kill normal humans/astartes and have an immortal primarch. All of these things could work but I thin k the best way would be for Vulkan to stay loyal until Isstvan V and the events of Vulkan Lives (SPOILERS FOR THE LAST CHAPTER OF VULKAN LIVES) after being tortured for months if not years by Curze, Vulkan is in a room filled with hundreds/thousands of his dead sons, in the book he escapes but what if he didn't? At this point the Emperor has restored his mind but it wears off after a bit so he reverts to a much more savage but grief filled state who just wants to be reunited with his sons. Trapped and surrounded by his dead sons Vulkan weeps and wails and rages at the injustice demanding that either he join his sons in death or that they rejoin him in life until on the 77th day alone with his failures a voice emits from every one of them offering to bring them back if only Vulkan will open himself to a new father and patron. Vulkan accepts willingly and sure enough his sons are restored to life but not as the proud sons of Nocturne, each awakens screaming as they are riddled with diseases uncounted. Vulkan stands central in the screaming masses of green armored Astartes as he feels his flesh begin to boil and bubble with the power of the rot that has filled him, alone in a room of raving madmen Vulkan does not scream, Vulkan laughs.
On the 777th day the doors unlock and out march thousands of putrefied and diseased but laughing Astartes newly christaned as The Reborn.
The Reborn: Post-heresy
ooook that got out of hand real quick lol
Is this the kind of thing you were looking for? (God I hope so
This is one of my favorite topics and if you'd like me to list the rest of the legions roles I'd be more than happy to.