Make it possible to let a player play 12 mins as PG substitute and 12min as SG substitute in one game.
That is part of the reason why managers prefer to use short roster: substitute players could play 12 mins in one game, which have litter effect to the game.
In the existing lineup system, starting players with high stamina will play even 45 mins.
Another point is substitute players should be able to help the starting players adjust their game shape.