From a flying stanpoint, not a legal or regulatory one, there is no reason one can't learn to fly in a RV 6. There is no reason that every trainer for a new student needs to be boring, bottom of the rung plane.

My good friend John Reyonds learned in the Navy, back in the 50s, flew combat missions in Korea and was a fine pilot. The first plane he was ever in was the SNJ (T6) he learned in.