How about we try this: Substitution on the fly!
Like in hockey. A player runs over to the bench and another runs onto the field. We would have to have another ref (the fourth official) to keep track - but we should have them anyway. Of course there would be unlimited subs. This opens up a whole new strategy, especially when pulling someone from the other side of the field that doesn't want to come off.
On the fly substitutions could help the game flow better, make it faster. Just my thoughts.
