I have a character who I specifically wrote to be a certain way. However, I want to rewrite the character to be different--weaker, and less independent in order to allow room to grow. How do I do this while keeping the character's identity intact so that the character doesn't seem like a new person all together?
Create a turning point, a defining event for this character, with elements of trauma. Here's an example:
John is as stable as a rock, he's very trustworthy and everyone at work depends on him. Nothing seems to scare him. Until, one evening, on his way home, he witnesses a young boy mugged by gangsters. This triggers a memory that was buried in his unconscious: something similar had happened to him, and with the past memories rushing in, uninvited, so does a forgotten, repressed sense of insecurity. Things are about to change, at work, and in his marriage.
You can rewrite him, but you can also look for other areas the character you have can impove.
Is he independant? That can lead to arrogance, boldness; so teach him humility. Is he strong? Not everything is resolved through strength of arms. Make him face situations where his power is useless. Situations he is unfit for, more generally. And there you'll find room for improvement.
I think the answer is in your question --you want to give this character room to grow. In that case, make the original version of this character the endpoint of the new version.
No one starts out life having it all together. This is basically the "prequel version" of the character, showing how he or she learned to become the strong, independent person you first envisioned.
If you want to develop (rewrite) a character's personality, just take it slowly. Normally, in books you will find the stereotypical farmboy-hero. You can see that in these novels, slowly the main protagonist gains confidence eventually saving the lands.
You basically want to do the same but backwards. If I were you, I would just totally tear his life apart. Everyone has their flaws, you need to find the flaws in your character, and open them up and make them bigger. This way we can slowly decimate him, turning good events into bad ones, causing him to become depressed and basically wrecking his life.
By doing it in multiple events like this, you can prevent the sense of "Okay my dog died now I'm so depressed I can't live." scenario's, which tend to be a bit unrealistic. Say your main character is arrogant, let his arrogance slowly consume him.
It's a bit like Anakin Skywalker actually. His character evolved from being one of good, to becoming seduced by palpatine into becoming a sith. Seducing your character might be a good tactic to try, actually.