How about a different theory on youth trainer. Basically youth trainer trains 18-19 years old as normal trainer one level higher.
So instead of world-renown trainer with fitness speciality that would cost you both kidneys you hire basic trainer with fitness and exceptional youth trainer for pennies and your 18-19 years old trainees would get exactly the same amount of training. And hiring youth trainer below your main trainer level is complete waste of money???
coefficients would be something like:
basic - main ~ 0.91, youth ~ 0.94
competent - main ~ 0.94, youth ~ 0.97
advanced - main ~ 0.97, youth ~ 1.00
superior - main ~ 1.00, youth ~ 1.03
exceptional - main ~ 1.03, youth ~ 1.06
world-renowned - main ~ 1.06, youth ~ 1.09