Your Soul Gem is the perfect phylactery. Even without a body, you are capable of conscious thought and can control your body without any range limitations. You can spend magic to create bodies for you to control. You can shape them to look like anything you want, be it human, animal, or monster. Each body has its own physical limitations, depending on how much magic you invested in making them. You can switch between bodies at will, or even multitask controlling several bodies at once. Your Magical Girl transformation is no longer reliant on your Soul Gem being with you, because of this you can now transform without needing your Soul Gem.
Additionally, you can crystallize your Karma to create additional Soul Gems that works as a decoy. You can store them in a safe place, or give them to someone you trust. Your Soul is in a state of superposition where the destroyed Soul Gem is not your main Soul Gem but instead a decoy. However, each time a decoy is destroyed, you lose the Karma spent on making that decoy.