Perhaps we have this backwards?

If there is something intrinsically valuable about controversy (and I'm not really sure that there is, but I'm willing to accept the premise for the sake of discussion), and we're not getting the optimal level of controversy on the topics we normally discuss (again, not sure I agree, but stipulated), then perhaps what we should be doing is not looking for "more and better contrarians" who will disagree with us on the stuff we have consensus on, but rather starting to discuss more difficult topics where there is less consensus.

One problem is, of course, that some of us are already worried that LW is too weird-sounding and not sufficiently palatable to the mainstream, for example, and would probably be made uncomfortable if we explore more controversial stuff... it would feel too much like going to school in a clown suit. And moving from areas of strength to areas of weakness is always a little scary, and some of us will resist the transition simply for that reason. And many more.

Still, if you can make a case for the value of controversy, you might find enough of us convinced by that case to make that transition.