i try to train 6 so they need 48 mins in one week(3games) which is a bit hard to manage with the playing time but at least 4 get full train each week....
plus 2 players on each other position ideal 72 mins each per week.
in total 12 players should be optimal for my type of training.
if you train stamina for example you could try to give 30 players a chance(nearly impossible to give the trainer the order to let the players play 24mins on position) if im not wrong with 24mins training time for stamina?
also you can do teamtraining like 15 players to train with 48 mins a week.
other thing you do some buizzinez on the transfermarket to get money, than you got more players and you just try to keep the stamina and form up.
i hope that helps to make your decision.
cu citb