"Would you believe me if I said the biggest problem I've had with this body was that some people find it difficult to punch a little girl?" By the time Carol had moved to her first homonculus body, her skill at alchemy was already undeniable. She had made herself a new body and gained a form of immortality, after all! Nobody within the ranks of the Illuminati could doubt her skill, and it wasn't until she had to interact with people outside of it that the troubles began.

"But well, being fit for purpose is a form of perfection as well. If a temporary change of form could get the reaction I wanted then it's worth it." Hence her adult form, meant to get the Symphogear to give her the fight she needed. Also if she wanted to buy wine or something.