In my opinion most stick designs could be used as trainers. On low rates and with an instructor present they can be perfect. It also may be a plus to use a stick so if the student does need help the instructor has a more maneuverable plane to get out of the mess, and is more likely to save it. I'm not saying that everyone should go out and get a stick but if you have some r/c experience and/or a sim, it may be worth it. I myself used a GP Big Stik 40 with great success. After a lot of time on a sim I had one flight with an instructor and (against his recommendation) went and flew solo anyway.

BTW- the Stik is still in one piece.