Doesn't matter if trailer is equipped with brake or not - if Subaru isn't designed to tow as per manufacturer specification, then it shouldn't be towing anything in the first place anyway even with modifications. It cannot handle the weight transfer in case there's any tiny mistake. To do so is criminal if people got hurt - IMO.
here's precisely why car shouldn't being towing anything bigger than small cargo trailer
[ame=http://www.youtube.com/watch?v=pmtZVD-stWk]YouTube - Car losing control on the road Poland‏[/ame]
when towing anything - it will jump or sway because of pothole, wind shear, irregular road groove, or cornering. When it does, a car does not have weight nor strength to correct it... it will just flip over or worse.
That way, the uneducated motorists in eastern Europe. Not in USA.