I want to do a mass roleswap in Evillious, starting with the Lust arc. The only thing I find noteworthy is how I intend to go about it, in other words changing as little as possible about the story to start with, then making the characters take different routes. In this case, I've decided to make Gumina fill Cherubim's role because of their similar backgrounds. Here's my pitch:
When she is nineteen, Gumina's plot to end her engagement is discovered and she is disgraced. Once an intelligent and desirable young woman, Gumina is criticized for rashly trying to get out of such a prestigious marriage, called stupid and careless. She has a slim chance of securing another husband due to her disobedience, and the Venomania family has little care for her now that they've been insulted. Gumina's freedom shrinks as well, and most importantly, she is branded as a slut who could not keep her hands off even the deformed servant of her fiancé. Finally, when she looks to Cherubim for comfort, he feels forced into agreeing with his family-- for once, he is not the undesirable one. Thus, with even Cherubim calling her a whore, Gumina becomes deeply depressed. Months pass before Sateriasis, out of pity, offers to marry her anyways. His family reluctantly agrees due to her own highly revered family, and Gumina, out of options, agrees as well. They are married quickly to avoid complications. A year and a half later, though, and Gumina is disillusioned with love, lust, and companionship and is ready to end her life when a witch approaches her and offers her a sword that will make her a "queen". Learning of the sword's powers, Gumina approaches Cherubim for the first time in months and hypnotizes him into killing his family. She then uses the sword to help him impersonate his brother, making him believe that he is Sateriasis, and begins building a harem.
The complication comes five years later, after Gumina has had several children, when she seduces Kachess Crim and obtains the Wrath Vessel. As it turns out, Kachess had been working with a young woman named Mikulia Greeonio, who caught his eye when she was able to vividly recall all the actions of Gumina and her abduction of a young man. Mikulia became somewhat attached to Kachess, and went to Princess Maylis to ask for help upon his disappearance. Maylis had become acquainted with Kachess's partner Elluka during this time, and the three formulated a to kill Gumina. One day, a young man with teal hair comes to the mansion, welcomed by Gumina. Once inside, however, he grows monstrous and slashes at her chest, exposing the knife. After a brief struggle, Mikulia kills Gumina after she transforms, and frees the men.
Kachess is impressed enough with Mikulia to consider her his friend, and the two remain close for the rest of their lives. Kachess also manages to keep his knife, which goes to Mikulia's children after his death. Mikulia moves to Marlon with his help, and marries a Marlonese noble. One of their descendants later marries into the Marlon Royal Family. Maylis meets a woman who convinces her to make a doll for Mikulia as thanks, in her image. Soon, after Mikulia is exorcised of the demon, the doll is abandoned and falls back into IR's possession.
Cherubim continues his life as a duke, and marries an Elphe woman who worships Held. One day, a chipmunk witnesses him praying to the tree of Eldoh and uses his face centuries later, calling himself Gast.
Toy receives Kachess's unwanted daughter, and her line leads down to Caleb Conchita and Germaine Avadonia.
Gumina's other descendants include Gumilia Venom and her siblings Tea and Gustav, Clarith Netsuma, and Gunnel and Nyoze Octo.
While Cherubim's arc was only a year, if I wanted Gumina to have multiple children, that wouldn't work. Incidentally, there are also less male Vocaloids, so in universe Gumina was simply more careful about the men she abducted, and didn't distract Tette from her work.
My main worry is how the characterization will work. Does this sound out of character for anyone? Critique is most welcome.