Hello,
I've been playing basketball for 30 long years.
I can assure you that a good captain, on the pitch or on the bench, helps a lot by keeping morale high and setting a good example for younger players. He also has the right to speak with the referees in order to have a civil discussion on their decisions.
I think a possible implementation of this feature could be interesting, but not primary given the huge amount of things to fix first.
Enjoy