You can watch and learn what the helpers do if you wanna learn some.
We have the age guideline for a maturity reason. Honestly, power in immature hands can get scary really fast xD
Secondly, if you try and expand staff too big, then staff really means nothing. Everyone is "staff" of some kind, and the boundary between player and authority is blurred.
Third, what criteria would you even use to choose trainee-helper? That would be more applications for Chris (probably 2-3x more than he already gets) and a very difficult time with all that.
Finally, what permissions would they get? Kick or ban powers? That goes back to power abuse and maturity. If not any power, then they just get to shadow staff chat... And might not keep things confidential.
All in all, because of maturity, workability and all the above reasons, I don't think this would work.
Lol. Went all hardcore debater there xD