If ET's are suppose to already abduct earthlings, then what makes you think they have not already chosen the right speaker. . ?

We couldn't send one person, we would need to send a group of people. I can't possibly think of one person that would represent everything of the Human race, let alone the whole of Earth.

If we took a person from each continent, at the very least, then we could send some kind of idea of what Humans look like.