Yes, Head Hunter
is definitely a major resemblance to Predator.
on the other hand doesn't look to much an Alien though. I do believe they can create an Alien skin for him by simply making his head longer for upgrading Void Assault, Giving him a tail that he AA's with and uses the tail for his Q. Void Spikes don't need to change too much since the aliens seem to have the same detail. As for leap whether they keep the wings or not it's whatever, but i believe they should get rid of them and implement the Alien's legs on to him. When he gains all 4 Evolution stacks he should undergo another transformation to make him look like the Alien Queen from AvP or the Hybrid from AvP2.