This is my first modder's resource, but hopefully not the last. :)
It's a simple script, some custom sounds and a slightly modified vanilla mesh so you can call a direct lightning hit on any ObjectReferences.



Function CallLightningStrike( ObjectReference akTarget, ObjectReference akSource = None, float afDistance = 2048.0 ) global

; Calls a lightning strike on the target straight from above.
; Optional akSource can be used to determine an alternate source.
; Optional afDistance can be used to determine the Z distance of the source marker when there's no akSource set.
; (Maximum possible distance with provided mesh is 2048.0)

; EXAMPLES:
; CallLightningStrike( BrahminRef ) -> a lightning strikes the BrahminRef straight from above from 2048.0 units Z distance
; CallLightningStrike( BrahminRef, GeneratorRef ) -> a lightning strikes the BrahminRef originating from the GeneratorRef
; CallLightningStrike( BrahminRef, None, 512.0 ) -> a lightning strikes the BrahminRef straight from above from 512.0 units Z distance


Papyrus source, modified vanilla mesh and 4 custom lightning sounds included (xwm format).
Mesh created from \Traps\ElectricalTrap\ElectricalTrapBeam.nif

If you want longer lightning arcs than 2048 units, you can edit the mesh in NifSkope and under the 3 - NiControllerManager node look for the 50 - NiNode called BeamEnd, and modifiy its translation value Y from 2048 to whatever you want.
Then under 55 - NiNode called LightningPower you'll find 56 - NiNode called ProceduralGeometry, and under that 23 - BSProceduralLightningController. Change its Distance Weight to the same value as well.

Then you might wanna change the distance of the Projectile within the esp as well. :)

CREDITS
KingTobbe, ousnius and Enai Siaion for pointing me into the right direction in NifSkope.