The most believable nico maki fan works for me are all either before Nico graduates or adults. As Love Live! went, Nico, in particular, became basically canon in her crush on Maki, if it were a het work like Toradora, that would have been obvious. That said, since neither show nor movie addressed how Nico and Maki could stay in contact after Nico graduates - and Nico's done basically nothing to prepare for life after high school, while Maki's already planning college, etc - It's a safe assumption in terms of Japanese themes and the show that they're NOT going to be as close. That's why there are so many stories, I think, about them parting ways and reuniting.
Re Kabedon: NOBODY Kabedons like Nico! Behold: https://dynasty-scans.com/chapters/nicomaki_days#16