I don't want her to be too uber-powerful. Powerful? Sure. More raw power than Xavier? Even that's okay. But she should still pale beside the likes of Cable, X-Man, or Franklin Richards, in my opinion. Her psychic power is what was so instrumental in allowing the former two to reach such outrageously high levels themselves. Chuck should have more finesse than Jean, too. In my perfect psychic hierarchy ("psierarchy," if you like), Jean would be able to blow Xavier's brain out the back of his skull in a pure contest of power, but Chuck would be so adept at psychic combat that he could sneak around in Jean's mind without her even knowing it.