I will try and put every character in the latest finished arc possible. That I have seen.

So for classroom of the elite, it will be them as second-years, after the island arc, with Kouenji finishing first, and Ayanokouji at 11th. Kiyokei will be canon. (Sorry for non-kei shippers)

Oregairu will be the end of the anime. So yukinoshita and hikigaya is also canon in this fic.

Kaguya-sama is kinda weird, I'll just put it at (manga spoiler) the aftermath of tsubame's rejection. After christmas and the festival arc. So shinomiya and shirogane are also together.

Bunny girl senpai will be at the end of the anime. Haven't watched the movie :/

e n j o y