What's the difference? You're just substituting aliens for God.

I believe that the difference is that Aliens would still exist in our creation, and therefore need a creator. God, since He exists outside of our creation, doesn't require a creator. (This is how a Theist would answer the "Uncaused Cause" question, anyway).

As for the "handwaving that science is still accurate", my understanding is that in it's pure form, ID doesn't say much about science at all. It merely asserts that based on the evidence of what we observe in science, the evidence demonstrates that it must have been created by an outside intelligence. ID also makes no claims as the the purpose or method in which our creation came about, only that it was caused by an external force.

Of course, this is actually saying very little, but it is the foundation upon which many arguments are made concerning God and creation. Still, the only question being addressed by ID is whether the universe around us points to a creator or a random occurance.