I'd love the phoenix to be used as a force of nature that genetically pre-disposed mutant can tap into ( this means Jean, rachel and maybe Hope) no different from how we have magneto and polaris tap into the electromagnetic force, no need to delve too much into the metaphysical or at the very listnot on a regular basis......so we have these 3 users able to tap into it (in different ways) due to their genetics as opposed to your run of the mill possessed host which has always been (and should be) a temporary deal.