I think the problem here is that Dark Void does not necessarily break sleep clause. Your opponent might have a lum/chesto berry, for example. Granted it is a very risky move, and most people would never use it, but it's still within the boundaries of acceptable attacks. Some players might use it by mistake, but it should be up to them to learn the rules of competitive play.
Regarding the sleep clause itself, I don't think we can really build an enjoyable meta game without it. You only have to look as far as environments without sleep clause enabled (PBR wifi, VGS) to see how over centralized teams become around sleep status. However, as there is a large disagreement over the issue (that cannot be solved in a mere discussion thread), I think the best route we can take is to just go ahead with the 2 week test. That way, if multiple sleeps do prove to be broken, we'll have (even more) solid evidence to back up our claims of adding a sleep clause.
In short, if you want sleep clause, try and break the game in the 2 week test.