Iceman is an omega level mutant who should be on the same power level with Magneto or close to Thor. As an almost pure elemental force, he should be present a challenge to Phoenix up to a point.
When Emma Frost possessed him, it was demonstrated that he could liquefy himself to slide beneath doors or seap through isolated/enclosed spaces, merge/emerge at different points of bodies of water(maybe even any point in any body of water anywhere), survive the destruction of his elemental body, and other uncatalogued feats.
He doesn't need to Phoenix out, but he should be recognized and seen as a formidable ally/threat in action.
Writers seem to forget to explore all the characters' powers, not just Cyclops/Wolverine/Jean.
Iceman should be so much more.