I won’t be surprised if they expand on this all next expansion in lieu of a new class / race.
Personally I think it’ll be a “new system” outside of glyphs in some way. Like how Druid forms and now the warlock demons are going to be customizable in the barber shop.
Glyph of the necromancer for locks to change their demons into undead.
That way the necromancer threads and posts can finally die.
If they end up doing this (or class skins) it’d be a perfect way to add classes to races when it lorewise might not make sense.
Like a void skin for Paladins/Priests that Void Elves could use.
Holy cosmetics for Lightforged SPriests & warlocks (I think summoning Lightforged demons / lightspawn instead of a voidwalker could be dope)
In THEORY they could even stretch it to allow other races to be Demon Hunters somehow.
I think "Avatar" spell for Warriors could get some nice actually avatar looking cosmetic glyph and not bronze looking poop, because that's how it looks like right now.
Something like Muradin from Hots avatar or just something more akin to dwarf racial.