I know it wouldn't really happen, but I still wish Hilda's ears was a toggle option for Hyurs.
As well as fang toggle for Miqo'tes.

Padjal horns are the same as having a Garleans third eye. For lore reasons you can't be them. NPCs would have to acknowledge that they are encountering a Padjal constantly in some way.
While Garleans can't use magic. Plus, outside of Cid most Garleans even defectors are still "unwelcome" to say it in the kindest way possible. So, a Garlean adventurer would have an almost impossible hill to climb.

Though it would still be great to have facewear of Padjal Horns, Third eye, ETC. Something outside the character creator one day.