First thing first, Astral Travel & Farsight can locate void, without the void player have no means to locate/travel to the other player. (Some issues with track, and config +autotrack doesn't seem to work)
My suggestion is to make him locateable with farsight in which area the void is hiding, but dont expose the room name leave that for trackers(rangers).
He lacks a pindown against supp recall my suggestion is implant a poison that acts like curse.
Some pros
Can use paladins lay hands
Can use basic red/yellow/blue potions
Can use sanctuary wand (Does those other wands even work?

He does gets immunity against spells, Which is nice, but it has its drawbacks. He dont get any spellups and loses so terrible in the late game.
My idea is to give him potions, make him be able to use brewed potions and found potions. It will create a market for potions for caster's to use and it will help the poor void survive late game. ( And if you make the change for potions, please remove the wands they are just silly to use )
And yes, I do think these changes would be reasonable comparing to the other classes. Without behing 'overpowered' or 'rigged' and could be fairly simple to implant