  Also, you note that Aviendha breaks the machine, but then you don't accomodate room for the idea that in breaking it she changed the inputs, she made it into something it wasn't...  When you "Break" your TV, is there any chance it will turn into a Crystal Ball that predicts stock prices? Or does something "broken" just quit working?  The Testing Arches and Testing Rings are distinct and are not solely Mirror World tapping. They mix Mirror World tapping, with TAR, dream bubbles, nightmares, etc., whereas I'd say the columns mix Mirror World tapping with Blood-visioning (and possibly other unknowns).  IIRC, the WO Apprentice testing rings is one of the ter'angreal seen in Rand's trip through the Columns. With a ter'angreal handy that shows probable futures, wouldn't it be easier to modify or reprogram that ter'angreal than to add that function to a ter'angreal primarily used to test ancestry and show the past?  It is extremely unlikely that the Columns showed that past by accessing Mirror Worlds, so it is equally unlikely that they can access Mirror Worlds for any other function/purpose.  While a person might be multi-talented, machines seldom are.  