Another theme might be redemption or growth. Maybe Deku, through his relationship with Bakugo's mom, helps Bakugo to grow and change his attitude towards Deku. It could also show Deku's growth as he navigates a relationship with an older family member of someone he has a complex relationship with already.
I'm not sure about specific 'deku x bakugo mom fanfic' offhand. However, you can try searching on popular fanfiction websites like Archive of Our Own. There you might find various works related to this pairing. Just use the search bar and type in 'deku x bakugo mom' and browse through the results.
Another theme could be growth. Deku is constantly growing as a character. In these fan fictions, his relationship with Bakugo's mom might contribute to his emotional or personal growth. Maybe she offers him advice or support that he doesn't get from other characters. And also, there could be themes of unexpected relationships. It's an unusual pairing, so exploring how such a relationship forms and what it means for the characters involved is likely to be a theme.
Toga could be an ally. Since she has her own complex relationship with the idea of heroes and villains, she might find Deku's transformation interesting. She could provide some of her unique skills, like shape - shifting, to help Deku in his villainous plans. Additionally, Twice might also join them because of his loyalty to Toga and his own sense of being an outcast in the hero world.
In this fanfiction, Deku's character development could be quite complex. Going back in time, he may initially be overconfident because he thinks he knows what's going to happen. But as he realizes that changing the past has unforeseen consequences, he becomes more cautious. He also might develop a deeper understanding of his friends and their potential, as he gets to see them at an earlier stage. He could start mentoring some of them, which would in turn make him more responsible and mature as a character.
Naruto's outgoing and boisterous personality would make Deku more confident. He would probably be more upfront and less shy. Naruto's strong sense of justice would also intensify Deku's already existing desire to help others.
I haven't read any 'Deku x Bakugo Mom' fan fictions myself. However, you might want to check out some popular fan fiction forums. There, fans often share and recommend their favorite stories. You can also look for tags related to these characters on the fan fiction platforms to narrow down your search.
The main differences are in their expressions and some minor details of personality. In the manga, Deku might seem a bit more intense, while in the anime, he's sometimes presented a bit softer.