Elves are like gnomes: tolerable in small quantities, but I'd rather not play play the game than play as one. In a world of a billion actually cool and creative fantasy races elves are like moldy wonderbread with a racial supremacy complex. Larian deciding that half of our companions must be elves is literally the most creatively dead part of the game and I'd love to be able to fix it. It's kinda untolerable to me that there's no proper dwarf companion for example. Yeah I know hirelings exist, but they're not really characters in the same way Karlach, Shart, Wyll, and the rest are.
Larian stated that the Magic Mirror won't be able to change race or body type of Tav, and can't touch companions at all.