For Celestia, her hyper aspect could be developed by showing her constantly pushing the boundaries of her magic. Maybe she starts off being able to do basic sun - related magic, but as the story progresses, she discovers she can use her hyper magic to create new sun - powered spells. For the futa characters, their development could be about coming to terms with their unique identity in Equestria. They could start off being a bit shy about it and then grow more confident as they face challenges with Celestia.
To develop Celestia, you could explore how her role as a leader is affected by her hyper and futa traits. For instance, she might face some opposition from traditional ponies who don't understand her new - found powers. This would force her to become more diplomatic and assertive at the same time. The futa characters could be developed by giving them individual backstories. Maybe one of them was an outcast before meeting Celestia, and through their adventures together, they find their place in Equestria and grow in terms of their magical abilities and self - esteem.