I'm still kind of experimenting to see which sizes I'm most comfortable with; I like 'em big, but I'm still now sure HOW big, ya know? That being said, I do intend to allow for more variety in sizes as the game progresses.
Drones in later chapters will add to that, for sure. Currently, all they do is affect the "Return to Diadem XII" ending, and her growth rate isn't really affected by anything outside of the story progression. I do plan on making the future chapters less linear, which includes more player freedom over X2's size!