The same way we have a skill tree for class, spec and now hero specs we could have a little something race-wise.
Now that we have cross faction groups and guilds it won’t hurt the faction balancing as much. It is true that we already have too many skills and our action bars are cramped, but I believe it is a separate issue.
Imagine being a worgen and actually using your claws. Opting either to contain your worgen side to unleash it as you burst or embracing your new feral nature as a constant passive bonus of speed and haste.
Mechagnomes would really have a swiss-arm-knife! As they can’t transmog arms and legs, it becomes an opportunity to just replace them with cannons and lasers for arms and wheels and gizmo rockets for legs.
The Human race-tree brings up their inner Vrykul or suppress it even more for a gentler, wiser approach. Humans choose between a diplomatic way for reputation and party bonuses, or instead they could go a lonely path to get a bigger buff to himself.
Imagine the Night Elf dilemma of attuning either to the dark or the light side of Elune. The Kaldorei also have a connection to nature, communing either with the dream or with the outward literal nature.