Coming back to an old suggestion by me: Speed should be more important. In the real world, good youngsters can compete with the very best, which is impossible here. The biggest activity between young and old players is their general speed.
I suggest the following two-fold change:
Young players start with a huge amount of speed, which decreases over time with their age. Via training, the decrease can be slowed down.
Speed is on the other side made a lot more important in the engine. This is supposed to reflect the fact that speed does not only mean ice-skating, but also the general speed of Puck handling and all actions on ice.
activity = difference
In general, I think it should be easier to incorporate youngsters into winning teams.
It could also mean that the amount of youngsters in the line-up affects the teams mood.
Or young players have some sort of "trust by coach" level based on ice time, age, and the league in which they play. If this trust value is high, they play a lot better than their actual AI.
Ideally this also depends on whether they play in a line with experienced players or not.