So how might acid blood work?
I'm thinking either a variation passive like Noxious Reptile, only it only does damage on hit. Kinda same concept, but irrelevant if you're the combo-er rather than the combo-ee. I guess to balance it they could make the acid blood do more damage than Reptile's stank? Another thing could be a risk/reward buff/debuff like Bane's venom, where you put a Damage Over Time effect on yourself that carries over to your opponent if you get close, and for more damage.
Another thing that would be cool for them to do, but I don't know how they'd integrate it, is a Shang Tsung-esque move where the Xeno somehow copies their DNA. Because Xenomorphs take DNA fromt heir hosts, y'know? The only thing I could think of for that is a whole variation where the Xeno just copies it's opponents specials from the tart of the match, but that seems highly impractical. I dunno, I'm not the person getting paid to think of these things.
All I can do is wait.