Agreed it´s more like they have unlimited reach of their powers and this also has been talked about with Monarch, Mister M and Franklin, they all are reality manipulators but on different areas or their power expresses itself on different ways and to address Magneto´s case, it´s been said repeatedly his main problem when his powers get a temporal short circuit has a psycological origin and not in the way his powers generally work.The thing about him is that he already has big feats but those feats can be even bigger in the future because his reach is unlimited and the only thing that holds him back is his internal fight over methods and means as well as his fear of losing his mind while using his powers.
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Now that I think about it, Franklin also has gotten short circuits of his powers after using them for an extended perioud of time or when he feels he´s been abusing them, same case with Jean Grey.
In the case of Lorna, I see her between Alpha and Omega, she has the same type of power Magneto has but we don´t know yet know if her reach is unlimited and when/if this happens then she will defintely be also an omega with or without Magneto on the list.
Now about Rogue, that´s also in question, because I think she has unlimited reach and it´s just that her powers work in different ways than those of Synch or Hope but of the three of them Hope is the only one considered omega.
I think the Omega label is still pretty ambiguous Hickman just added some rules to the category so it made a little more sense.