I can shed some light...

During MKX development, a good friend of mine named Justin "Goby" Fields was working on a couple characters for NRS. He owned IronKlad Studios in CA. I think he is at "Sanctorum Studios" now. Anyways, I only remember 2 of the 4 or 5 he was working on, Jax and Quan Chi. Those 2 weren't shown publicly yet and he had signed an NDA. He showed me because I am a super fan, and he wanted my feedback. All that was around 7 years ago. And in all that time I have never seen anything that refers to what the skull on Quan Chi's chest actually is.

Like I said, I am a huge MK fan, especially the lore and trivia, and the main thing that stuck out to me in all the designs that was new and unique was the description of the skull on Quan Chi's chest out in the side margin of his character render. It said that "the skull belongs to a very powerful VAMPIRE." The thought I had at the time was, is this a nod to Kahil Grigesh? I have no idea if this was a design element that NRS told him to incorporate or if it was something Justin came up with himself.

If you go back and look, it is pretty clear that the skull has giant vampire fangs on it. Plus, vampires have a way of coming back to life, cutting the head off and carrying it with you would be a pretty good way to make sure that never happens. I have no idea why the eyes are covered. Keep it "asleep" or unaware of its location I would guess.

I don't think it would be hard to track Justin down and get an interview and see what he remembers, but for me, when I first saw the Quan Chi reveal and he had that costume I thought "This is F-ing too cool". But, for 7 years, all we hear about this plot element is "crickets". It's such a cool little "seed" that was planted with that costume design and has been hidden in plain sight this whole time. It would be a shame if nothing ever comes of it. But, if nothing ever does come of it, I think "a nod to Kahil Grigesh" or even "Vampires" in general is the best way to think of it.