I agree on power boost but not on Iceman’s level.
Sue is and should always be the most powerful of the original four.
John should be stuck in this form for a looong while. He should be able to learn other flame forms for once , blue, white, even a fictional green, etc.
He should explore heat absorption more by absorbing all of the heat around and freezing a room or opponent.
He should go back to making duplicates.
But again, not god like powers.