But besides the fact that extraterrestrial life is highly speculative (as there is no evidence) you are still left with the problem of where did the extraterrestrial designers come from in the first place? Wouldn't they have had to evolve themselves? It doesn't really answer the question of where intelligent life came from.
True, it doesn't answer that question. But it might answer where OUR earthly life came from. And it would close the case for theism - at least on OUR planet with OUR religions and OUR 'holy books' :)
And since you mention Space Odyssey, it's more or less what's behind the plot of Carl Sagan's "Contact".