Oooh, very cute. Makes me wonder what that crossover would be like (aside from an absolute massacre)?
I have given this a lot of thought, actually. Of course, the crew would be a squad in the Survey Corps. Sigrun would be the leader, and Mikkel would be the only remaining member of her squad after a mission gone horribly wrong. Mikkel has been in the military a couple years longer than Sigrun, and as such was the squad's initial leader. But after the failed mission, Mikkel was more than willing to step down an let Sigrun take charge, partly because he recognizes her talent, and partially because he can't bear the thought of being responsible for more of his friends' deaths. Over the last few years they've lost several people, but many of their squad members have also moved on to leading their own squads. This year they've gotten three new squad members, straight out of the training corpse.
Lalli And Tuuri come from one of the northernmost districts, right inside Wall Maria. Most of their family died from a disease that ravaged their district when they were young, and they have been staying with Tuuri's older brother ever since. Onni is in the Garrison. They've never had a titan attack in their district, and he always told Tuuri and Lalli that they were safe in their little town. Onni has not been the same ever since they were forced to abandon Wall Maria and move inside Wall Rose, always afraid of being attacked by the creatures who stole from them the home he thought would always protect them. He is, of course, less than pleased when Tuuri and Lalli join the military. Neither of them has ever seen a titan, and they have no idea what they've just signed up for. Tuuri says she wants to help reclaim their old home, and Lalli joins because she asks him to. Tuuri struggles a lot with her guilt about making Lalli join, as she begins to realize the horrors that await them outside the wall.
Emil's background is completely different. His family lives inside wall Sina, and up until a few years ago they were highly esteemed amongst the elite. That all changed when his mother was proven guilty of infidelity. As his parents tried to patch up their marriage as best they could, their social status plummeted, and with it crumbled his father's business. In order to restore the family honour and to secure their sheltered lives in the capital, Emil joins the military, intending to claim a position in the military police. However, despite proving himself a natural talent, Emil doesn't end up in the top 10. This is largely due to him being considered too rash in his actions, as well as his leaders considering him "unreliable". His fellow recruits tease him, saying "unreliable" is really just another word for "cowardly". With his pride wounded and his one shot at providing his family taken from him, Emil joins the Survey Corps, vowing to "prove them all wrong". This is, of course, an act of impulse, and he regrets it almost immediately (and spends many a day after that regretting it quite LOUDLY).
Also I'm playing around with the idea of letting Reynir be a titan shifter, because come on. That would be totally hilarious.
PS: This post is probably all over the place and also full of typos and weird mistakes. It's 02:40 here. I'm sorry.