I would love developing more CR with Fuu! She's so friendly and sparkly, I love her. I'd be up for some comforting and friendship in general. I think it would be good for Kobato to have some girlfriends around her own age-ish that could maybe go out and do things with her.
Since she mostly just goes out and finds situations herself. It might be fun if she had an actual planned outting to do something fun or exciting, and the two could get to know each other better.
ALSO SHE NEEDS A GIRL TO TALK BOY TALK TO. Outside of...Mom and Dad.