New races offer new customization options. The things is, many of the new "races" have rather limited customization options.
Think of the Yellow Draenei, also known as Lightforged. Three male faces isn't much!
It's already too late to change this, but maybe instead of future allied races, imagine how it could be done:
Achievement/story progress related unlock of customization features
"Congratulations, you unlocked the Mag'har visuals for the Orc race."
^ the same could be done for Kul Tiran male/female looks.