I'd be more concerned about the enormity of Vivi's Death Flag. They've been foreshadowing her impending death so heavily, that they're bound to use it as some "twist" or another. Maybe she'll turn out to be another Chaika who somehow forgot about it! Her eyebrows are thicker in some shots...
Whatever it might be, they've been leading the audience along just a bit too obviously for me to fully trust it.
Fredericka definitely got taken out because she was too wound up about her impending fight with Tooru. Others may disagree, but I am fond of the idea that though they have this nearly immortal dragon-beast who can transform and all manner of other advantages...is fickle and is more than likely to go off and do her own thing instead of helping them. It gives the author an out instead of power creeping the protagonist team too early. She also desperately wants a fight to the death, making her allegiance to them dubious at best.
@shinta:
Akari has been talking about having Tooru stuffed since the beginning.