Imagine that Dr Morse ends up in hell and Alastor does not fw him
Yes he is a murderer himself but he went after people who he saw as bad the Dr did all his shit to people who were innocent and took advantage of most
Al and Morse constantly beefing
Alastor is a monster and proud of it, but he is a monster with standards.
Also, Morose starved his pet Nessie to the point of attacking anyone she saw out of desperation, despite her having a naturally gentle personality. As someone who no doubt had to go days without a proper meal in life due to the time period he lived in, Alastor would find that especially loathsome.
Considering the obvious Lovecraft inspirations, I wondered if Morose would've sold his soul (and possibly some of his victims's) to Frederick Von Eldritch during his rituals and is now stuck as an eternal servant to the family. It think his sinner form would include scaly skin, his moustache replaced by fish fins and the tentacles from his experiments replaced not just his legs but his hands too. I think Hell would have his adulation for his more eldritch body turn to hatred or horror.
Samantha was just as involved in the cruel experiments until her passing, so despite her regrets, she is likely also in Hell. I don't think she was personally involved with the rituals, so her soul is free after passing on (at least at first). Considering her devotion to her husband even after seeing the monster he's become, inspired by the original Fullmetal Alchemist anime I think she would be cursed to be unrecognisable to him.
Despite his hand in taking the Mad Doctor down, he also stuck around longer than the other assistants (partially out of madness and obsession but eventually out of fear) and took part in experimenting on his fellow scientists. So he would likely be sent to Hell after death too. His sinner form, I think, should be a dog sinner because his loyalty to both his sister and Doctor Morose's cause was ultimately what led to him falling to Hell. Because of his curly hair, how about a brown barbet breed?
For Howard I can see two options:
He becomes a winner, but once he realises that Philip was in Hell he would follow, refusing to lose him again, becoming a Fallen Angel. I think his experience on Great Maw means he's more likely to succeed than Sir Pentious.
He becomes a sinner because of his deal with Knowhere, who would be a benevolent demon in this case.
Because of his connection to Nowhere, sassy and clingy personality and to contrast Philip, I think Howard should be a cat winner/sinner. He could share Nowhere's prehensile tail (that he sometimes gets stuck in the door!) and makes ear holes for his cat ears.
I am unsure about how involved Angelique was in some of the crueler experiments since Morose locked her away after Samantha's death, but I'm inclined to think she went to heaven and studies under Archangel Raphael for her breakthroughs in healing. Imagine her managing to grow whole new limbs for Vaggi, Lute and Emily!