So I figured I might as well drop this in here despite the decision pretty much already made not to have her in the team. If anything it might serve as a template for any other potential applicants. Or it might change their minds. Whatever it is, it will help. Somehow. I'm going to stop rambling now.
Name: Jocelyn
Thyil Antiqua
InteractionsSetsuna: Safe to say that these two will easily get along perfectly well. With both personalities along similar lines and being related, there's a natural bond already formed.
Anna: Having another female member on the team should be in the interests of both Anna and Jocelyn. Being a girl should make getting to know and socialising with Anna that much more easier than the other two, and vice versa. May be able to make Anna open up further to the team. Maybe.
Calen: Potentially the worst matchup out of the three, but plenty of opportunities to make banter and jokes at Setsuna's expense. Or it could go the other way with Jocelyn stopping Calen from verbally abusing Setsuna/Anna.
Overall/Combat: The peacekeeper in the team. Can half-fill the deficit of range in the team, but more suits the role of support medic.
As mentioned in previous spoiler, only a baseline template for other applicants. I do not expect this to be accepted, only to show what might happen.