Seems somewhat redundant then since the Supreme Being is by default the most powerful being in the Everyverse.
Which is not to say that a being from another Everyverse couldn't find their way into its domain.
It's not to say that one SB might be all that powerful in comparison to another one, after all - one Everyverse might have Tetragrammaton as the Supreme Being, who wouldn't even hold a candle to Logos. Of course, the situation might be a bit more complex than that - but then, if it wasn't, they wouldn't be Supernals, now would they?
Also, I wouldn't say that by default the Supreme Being is automatically the most powerful being in the Everyverse - after all, it's more than implied that even they can be defeated by beings from within their Everyverse, even with all of their defenses (including having the Lipikas defend it).
Delving back into some of the older records, with a mild burst of inspiration...
Metaphysical (Ex) [Metempiric]
Your existence is empowered by the Akasha.
Prerequisites: Infinite Constitution or Infinite Charisma , Transmortality
Benefits: You can never be destroyed. Even if you no longer qualify for this ability, you do not lose it.
Special: Although a Supernal with this ability would not necessarily have to surrender, even to a more powerful opponent, it is not unusual for those who have been bested to quietly serve those who have proven themselves the better terabeing.
Metamerism (Su) [Metempiric]
The Akasha will not relenquish you so easily.
Prerequsites: Cha 750 or Con 750, Transmortality, Omnidimensional.
Benefits: If you would be destroyed, instead you gain another manifestation.
Eleventh Sense (Ex) [Metempiric]
The Akasha has revealed the scope of what lies beyond to you.
Prerequisites: Alertness, Eighth Sense, Ninth Sense, Seventh Sense, Sixth Sense, Tenth Sense.
Benefit: You are able to scan beyond your Everyverse to determine potential threats. The DM shares his thoughts and insights into your new slew of extra-Everyverse enemies and how to defeat them.
Perfect Dominance (Su) [Metempiric]
All beneath you bow to your slightest whim.
Prerequsities: Cha 750, Dominance, Greater Dominance, Superior Dominance.
Benefit: Opponents with less than your hit die automatically fail their saving throws against any of your attacks.
Some of these abilities are obvious extensions. Metamerism was an ability that you talked about previously that was never quite written up. Technically, there's almost no reason for a Supernal to have both Metamerism and Metaphysical - they're more meant to be picked, one or the other. Which is picked depends on the style of the Supreme Being involved.
*shrugs* Then again, most of the Metempiric Abilities are just mild thought experiments. That being said... thoughts?
Edit: Now, a thought occurs to me - as Time Lords exist outside of the scope of reality as we know it, then shouldn't they be able to transcend the weaknesses of portfolios, in a way? If so, what level would such an ability be? Transcendental, as marked as normal for Time Lords to have? Omnifics, which are esoteric for Time Lords? Or Metempiric, which are restricted to Supreme Beings/Retired Supreme Beings (people who have had access to the Akashic Records at some point)?
Honestly, I could see a case for any of the three.