Theoretically, it's entirely possible. However, the Turing test hinges on being able to perfectly mimic the responses you would expect from a human being, and having a machine simply draw responses from a pool of preprogrammed answers just wouldn't be as smooth as if there were an actual intelligence. Of course, what is human speech if not drawing responses from our own little internal wikis? I don't really know enough about computing to give an informed opinion on this, but you're definitely on to something here. Cheap trick, but definitely something.
What'd really amaze me is if the machine you propose goes on to get the extra credit in the Turing test: Not only convincing the operator that he's talking to another person, but convincing the operator that he's a machine.