I mean, they are not a culture or a race, at least not in Warcraft. They are just individuals who integrate with either elf or human society. If we had subraces instead of allied races I could see Half-Elf as a Human subrace and it could still be done as a Human customization; add a few faces that are a bit more angular (I think the actual shape of the face cannot change but you can do miracles with a bit of contouring), add an option to have ears equivalent to short elf ears.