I think Kairi's problem has always been that her movements in the story have always been very restricted due to the plot that was happening around her. She was only capable of being present for three games, and in all three for one reason or another she's been quarantined from the rest of the cast.
Now that we have a fresh start in the new saga, and Sora's MIA, there's huge potential to make Kairi a more proactive character and recapture the cheeky, irreverent and adventurous girl she originally was. That side of her was put on the back burner in KHIII but I think now's a good time to bring it back.