Thanks to those who've reviewed my first idea, and glad that at least one of them liked it. Hope to see it used for a story! Here is a second idea that has been nagging at me for the past couple of days, hope it's well received! Got this idea from reading a story about Yukari waking up and finding herself in an alternate world.
Idea #2: Shiho's Wish
Shiho Nishizumi is a strong and confident woman. Never showing emotion, and always seemingly cold to those around her, even to her family. But what if there was a side to her that she kept hidden? A side that she will never show to others for it goes against the very tenants of her family's school. She loves her daughters more than anything else, even more than Tankery. But she has to keep it hidden, keep her emotions in check, otherwise she would besmirch the Nishizumi name. On the night of the last day of the tournament, after Oorai had won, Shiho collapsed into bed, feeling extremely happy for her youngest daughter, but was having to hold back tears because she wasn't able to be there for her daughter when she needed her the most.
Crying herself to sleep, Shiho made a wish: "I wish I could've been there with Miho from the start, to experience everything she has, and to be someone she felt she could come to for comfort and advice." Next thing she knows, she is waking up to the sound of an alarm clock ringing loudly in her ears and someone banging at her door and calling out to her. She gets up, shuts off the alarm, staggers over to the door and opens it to reveal a girl, who looked very familiar and was wearing her daughter's school uniform. "About time you woke up, Nishi-dono!" exclaimed the bushy brown-haired girl as she entered the room and pulled Shiho after her. "We're going to be late for our first day of second year if we don't get moving!" Pushing Shiho into her bathroom to get cleaned up, the girl continued chatting away excitedly. But Shiho didn't hear a word of it, for she was staring at her reflection in the mirror. A reflection that she hadn't seen since she was in high school years ago.
And there you have it! Shiho goes to bed an adult and wakes up as a teenage girl Miho's age and she's also a student of Oorai. She's still a Nishizumi, but she is part of one of the clan's branches, the Nishi. In this way she is Miho's cousin, and she gets to be a part of her daughter's life. There is still an adult Shiho, so she has a different name, I leave that to the author to choose. Oh, and if you can't tell from the description or the way the girl talks, Shiho is friends with Yukari! Who better than a girl who loves tanks. So, if there is anyone who would like to make this into a story, please do so!