Kind of a side note but...

If unranked ever gets officially added to WoL it'd be a prefect solution to this kind of problem.  But I suppose we can't assume that ever gets around before HotS comes out.  

I guess the next best thing to biting the bullet and taking the losses to your rank would be to get a good friend who is better than you and play Zerg against them until you feel semi-comfortable with it.  

That or creating a smurf I guess.