Glacier 1900, Training FOs were introduced a few years back as a way of expanding the Training Dept and providing cheap training for SOs. It hasn't been too successful - some of those that volunteered were there more for the power trip than any real interest in training. By all means show a long-term interest in training during your interview, but I wouldn't get too hung up on the T/FO thing - they might be suspicious of your motives!