Storm Call is my favorite ability. This upcoming league I will be committing fully to it. For reference here is the scaling change from the Manifesto:

Storm Call: Now deals 21 to 39 Lightning Damage at gem level 1 (previously 21 to 40), up to 949 to 1762 at gem level 20 (previously 640 to 1188). Now has 250% Effectiveness of Added Damage at all gem levels (previously 165%).

I'm considering Trickster Harness the Void triple conversion (Lightning > Cold with 2 Shaped Call of the Brotherhoods. Cold to Fire Support. Eternity Shroud + whatever other Elemental to Chaos sources I can find) stacking Added Lightning Damage and then using Soul Ripper and The Traitor Keystone Passive from Brutal Restraint for Flask Charges (Go CI and get a bunch of ES Leech) for as much uptime on Vaal Storm Call as I can manage. 6L would likely be:

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Vaal Storm Call

Less Duration (essentially mandatory for the base version of the skill)

Trinity Support

Cold to Fire Support

(Awakened) Added Lightning Damage Support

Spell Echo Support (Possible this isn't ideal but probably still best 6th option)

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4L Wither Totems (Wither > Spell Totem > Multiple Totems > Faster Casting)

Herald of Thunder + Auras (Probably Grace/Determination since they dodged nerfs)

Skitterbots if I can fit them in somehow or Aspect of the Spider

I think the new base gem scaling will absolutely make this top end viable but I'd appreciate thoughts if this seems like a foolish enterprise.

Harness the Void isn't the most popular Ascendancy skill but I've always enjoyed it and Trickster has been my favorite ascendancy for awhile despite being nerfed considerably recently. Harness the Void, though worse than it was, still seems very good especially for this kind of concept. I appreciate your thoughts.

EDIT : Hastily put together end game version (though not anywhere close to being optimized I did this in about 10 minutes - this would be a version that is not all in on Vaal Souls with Soul Ripper) PoB https://pastebin.com/W7MRhHNL

The additional Added Damage Effectiveness of the base gem is NOT considered but I tried to add the difference in the gem levels as added lightning damage in the configuration.