Actually the best way to identify rapidly improving young player is to measure the improvement in the 12 month period leading up to the deadline. Consider two juniors both at 2475 at the deadline. One started the year at 2450, the other at 2350/ It is quite likely that the player who started the year at 2350 is presently the stronger player.

In any case fielding the strongest team possible probably means that player #5 only plays 4 or 5 rounds.