I just read Excalibur #61 for the first time. It is about Rachel Grey recovering and healing in space cocooned in Phoenix energy when she meets and spectacularly fights Galactus.
Honestly, I take it back that Jean should have the Phoenix Force. As gorgeous, mystical, and frightening a Phoenix host can be (if done well...I miss you Grant Morrison!), this comic states that the Phoenix takes and steals its energy from "life yet unborn".
Here the dialogue for everybody who does not know what the Phoenix Force bound to a host really does and that Galactus and the Phoenix are not that different:
Phoenix: In mindless passion I destroyed a sun and a world it warmed. I acknowledge my sin and bow low beneath its burden.
Galactus: I do not speak from a single sun, but of that from what you steal your powers.
Phoenix: I have no need to steal-I am the emodiment of life.
Galactus: You are indeed unique. Born of the void between states of being. But you are an expression of the universal life force. Not a well-spring. The universe is finite. In the moment of creation, all that will ever be, was. In birth and death there is transition...and in lifting, advancement but nothing new is created. Life must feed on life, you are not no different.
Phoenix: I am sustained by the warmth of life's fiery cycle.
Galactus: In you natural state perhaps, but it is not sufficient to maintain your activities on this plane. [...]
...you are neither weiry nor hungry, because you tap into a source of near limitless potential. The sea of life yet unborn."
Maybe the goal is NOT to have a Phoenix host at all...I'm not sure how to interpret Galactus words "activities on this place" but I understand it as the Phoenix Force bound to a human host starts the process of stealing "life yet unborn". I think Wanda and Hope where up to something when they tried to disperse the Force and Hope rejecting it.
The early narration of the book also gives a vague explanation why the Phoenix Force seeks a host: "A celestial consciousness as old as creation-Forsook godhood in search for purpose. A reason for being."
677742-rachel_vs._galactus_006.jpg
Maybe we need a storyline where Rachel and Jean once and for all return the Phoenix Force to its natural state and forces the Force to become a transcendental being without a host again.