This but make it optional. I know it’s not what you’re going for but I think it would be a compelling divergence for those who choose to embrace the void energies and the whispers and those who decide it was unwise and wish to take up the old ways of their people before the void, before Kael’thas and the fel and join the silver covenant. Basically it’d be a “return to nature” like movement, they’d reject both the corruption of the void as well as the lack of wisdom of their kin in Silvermoon over the years and embrace the Silver Covenant. Unfortunately I just cannot see Blizzard “destroying” a playable race entirely so this choice also lets them off the hook. For that matter it could require one to go through a questline just like unlocking void elves to unlock this choice which would further gate it from people which seems to be something Blizzard wants.
Of course one drawback of this solution is it still would not permit players who want to play for example paladins as high elves to do so owing to void elf racial restrictions.