kewl! very, very neat.
now, if an alien walks on two legs, has a torso, two arms, one elbow each, one head, two eyes - does that lock us into the opposable thumb scenario? This design for the aliens makes a very interesting broader implication: that evolution for all air-breathers follows roughly the same lines - start as a lizard, a monkey, or whatever - and you end up with forward-facing eyes, dedicated pair of legs for running and arms for tools, with roughly the same proportion to the rest of the body. Even if this was dictated by game mechanics, I think this can be easily worked into a story line.