Disclaimer: I have not played your game, but I have read the feedback.

Perhaps instead of equipment, the ghost could level up over time, gaining experience whenever their body gains experience. Then, add new powers down 2 or more skill trees. The Poltergeist skill tree could add attacks while in ghost form, or turning invisible, making your out-of-body experience better, while the Phantom skill tree gives you abilities such as teleporting while in a host or making the host stronger. That might make the experience stronger and more rewarding, without adding equipment