Find your tribe in a Sea of Creativity
OKAY OKAY OKAY SO HEAR ME OUT
Akechi as a Velvet Room attendant au- but he effectively replaces Caroline and Justine in Ren's Velvet Room.
So basically: During one of Wakaba's questionable experiments, Akechi dies, and Yaldabaoth is like "Fuck, I can work with this" and scoops up Akechi's soul into the Velvet Room to act as Ren's attendants when the time comes. The whole 'splitting in half' thing was barely even Yaldy's doing in this au- Akechi's personas were already Robin Hood and Loki, so when he was dragged into the Velvet Room post-death, he manifested as two seperate entities.
Back in the real world, Wakaba's reaction essentially boils down to "shit", since she just murdered a child by mistake. Shido would normally be very upset by this, but he instead decides to make it work, and instead of having Wakaba killed, he blackmails her into complete compliance by holding her ethical malpractice over her head. Somewhat unsure as to the state of the mental shutdowns- definitely no psychotic breakdowns, though.
Meanwhile, in regard to other canon divergences- Futaba doesn't have a palace, but is quite upset with her mother due to how obsessed she is with her research, especially since all the stuff with Akechi. (Futaba is unaware of all this, for the most part)
Wakaba, on the other hand, does have a palace. Perhaps focused on guilt +deflecting blame?
Sae's role in the story is fairly similar, but rather than being on the mental shutdowns case (She might still be on the case, but it isn't her focus/leads into what she's actually interested in) She's obsessed with Akechi's missing person's case, since she noticed it two years ago and how suspicious it is, and is furious that no one seems to care, a concequence of Shido's influence and the general poor treatment of orphans.
So, yeah. Brainworms. ¯\_(ツ)_/¯