This was an absolute labour of love, one that I swear I bit off more than I could chew several times. I hyperfixated like a madman and spent fourteen straight hours working on this.
This is an upgrade/update to AltimaB's Crystal Skin which applies the crystal to the body, rather than to gloves that you need to apply. This means two things: One, that you need to have TBSE installed (and applied) to the character you want the crystals on (...the Exarch, presumably), and two, that it should show up in cutscenes, or if you change his clothes! The third photo on this shows the priority order that your mods should be in for this to work - in short, this must be ABOVE any of your TBSE files. Additionally, it ONLY works with the TBSE default chest - you will notice I am using TBSE-X legs, and using the Body Type Edits file over that to return to the default torso.
I have made sure that almost all of the original texture options available - the only one missing is see-through, as by the time I finished this I couldn't figure out how to get it to work for my life (on purpose - I had the see through show up PLENTY of times while testing textures).
All three of the Exarch's outfit game files have ALSO been modified to use this crystal, rather than the vanilla crystal built-in to the outfits! This means there should be no neck seams, and any of your selected textures will work. The only exception is that the 'final' outfit (where the crystal progresses) only changes if you use the Zodiark texture, as there was an extremely minute difference between all of the other options due to the sheer glow.
There is a toggle for hiding ear flaps, should you wish to use an ear replacer! I personally use MiKitten Ears on my miqo'te, and having noticed that the Exarch's robe hides the ears (as a result of hiding his tail), I have also made Crystal MiKitten (downloadable as a variant), which is literally just replacing his hair + vanilla ears to be hair + mikitten ears. I do not know how these will do with animations, though their bones do show and work normally in gpose!
Massive thanks to AltimaB for their original mod, again, as well as Longerrpigs for the Libellule mod that AltimaB worked from!