I would say on paper, the idea was pretty good, and I think overall, if you use it they way you would any opportunity to learn, you can certainly improve using the guidebook.
From what I understand the TMS Overseer is a newboy position because it took so much work, the body couldn't wait to pass it off to the new appointee. Unfortunately, it was not the right position for some, and the congregation suffered for it.
In the big picture, if as kids we were encouraged to participate in school activities, clubs debate teams...I think most of us kids would have benefited more than a 5min presentation in the TMS. When I quit the school I told the overseer "I graduated."