Well my autistic brain just started coming up with this fanfic of a dlc route for a more happier scenario of Takumi following Sirei´s order to come back to 1st defense academy.

shortly after day 20, maybe a new decision comes up that somehow leads to a Hiruko and Takumi from an alternate timeline, not the S.F one since Hiruko didn´t give two fucks about fixing the retsnom timeline, burning the library or at least that specific book, so this version of Darumi Takumi, and Shion never discover more information about Retsnom and its location

Maybe after hearing the constant shit from everyone about whining not having enough fighters, and Takumi getting so much shit thrown at him, he and Darumi just say fuck it and leave the school. Maybe it´s just them fending for themselves in the ruins for 80 days. Takumi can actually get to know Darumi without anything going wrong. With a final decision at the end leading to two endings, one is going back to the school to the escape shuttle (probably a bad end since the academy is likely fucked and everyone else is dead), and the other is just them deciding to stay and live on Futurum. During this 100 days, we´ll probably see them run into the commanders and Kamyuhn and we could get to learn more about them

Could probably be called survivor route or something. Could also be a cool challenge mode route since you´ll only have two sdu members and you have to beat every battle, including commander fights, huge waves of enemies, etc, without dying since they´re are no recovery drones

We´ll have to wait how they handle dlc, if it´ll be a new clean slate like Takumi time traveling again with a cheaper version of second scenario in 3rd scenario, and that has a bunch of new routes, or if they do add new branches to already existing ones