How about this:
https://i.ibb.co/c2xJCNV/subrace-customization-mockup-highelf.jpg
We do not even need any new racial skills: just an alternate demonym connected to an optional customization template and a quick line of text based on the NPCs currently in game.
“Curious to learn more about the Void, some High Elf Wayfarers have joined their transformed kin.”
(Credits to Moira for the mockup art of course)
Edit: and if the racials are really an issue, they could get a customization glyph of some sorts just as shadowform can have different intensity for the spriests?