It is a cool concept, I'll give you that. But it is also a bit of a stretch when it comes to the restrictions on foci and their creation.
You essentially have two options: Implant or Tattoo.
As an Implant, it is somewhat redundant, since the character already has the Fangs/Bite, and he doesn't need an implant to gain it. It also has the drawback of costing Essence, which is usually the opposite of what you want as an awakened individual.
As a Tattoo, the rules are a little vague what the process is. We don't know if the subject needs to be present for the full enchanting process or if the tattooing ink is enchanted and then just inked. Either way, though, the tattoo would be pretty obvious, probably a decent sized facial tattoo around the mouth.