I think I may have found a plot hole....
If you kill an undead person and then perform a perfect ressurection on them with the light, would that make them living? Since ressurections attach the soul back to the body completely while undeath is an imperfect soul.
This is without taking to account that ressurection is extreemly difficult lorewise by the way.
Also, what would happen if a void elf was lightforged? Would they blow up or would it perhaps work? I'm genuinely curious now.... would a void elf going to lightforged be like how a naaru can be 'redeemed' from the void to the light and vice versa?