Are bumps allowe?
The "girls in Anime in general" discussion already took place somewhere else, so I won't go into detail here.
That your team lacks a tank could be a problem, but mustn't necessarily.
Celia can defend herself pretty well, especially if you invest into mirror stance.
Alessa Raincross is the best sniper, since she doesn't need to close and has a high range, thus preventing your enemy from attacking her After depleting her actions for the hidden attack.
Feng Yi can be quite powerful IF she manages to get her combo off, a clock might help here to keep her alive (dodge action, for example) in case your opponent still stands after your combo.
Kujaku Hime sounds good to me to take out attackers and do not underestimte her ability to move through difficult terrain without slowing down. In several tabletop armies this is worth a ton of gold if you leanr to use it right. Her poison effect at 13 isn't the world, but could be devastating to Kronen, for example. Serum is definitely worth ist' 5 levels. I do not have had any experience with her on the battlefield until now, so these are only suggestions, but she is defeninitely one of my favorite characters thus far.
All said your team IS pretty balanced, having two range attackers, two flank runners, three defenders, 2 exhausters, one sniper the only real problem is to get it going. I think this could take a while and a good deal of experience, but this team can easily become a versatile nightmare for your opponent, because he doesn't know what to do about all these vastly different characters.
Maybe spreading out is a nice idea, especially against tank lists, so your opponent needs to split out as well.