One idea could be that the female Kyuubi form uses her unique powers in a way Naruto has never thought of. For example, she might be able to communicate with animals in a more profound way due to her connection with nature as a nine - tailed fox. Another plot could revolve around how she has to hide her femininity while in the Henge form to avoid unwanted attention in the ninja world. Maybe she struggles with maintaining the balance between her human - like emotions and the wild nature of the Kyuubi.
A possible plot is that the fem Kyuubi in Naruto's Henge form starts to develop her own relationships in the village. She befriends some of the younger ninjas and teaches them things about the power of the Kyuubi in a more gentle and feminine way. This could lead to a sub - plot where some of the older and more traditional ninjas are skeptical of her methods but the younger ones thrive under her guidance. Also, she could have a love interest that is initially scared of her Kyuubi side but gradually comes to accept and love all of her.