1. Once the gk is over halfway line he effectively becomes an outfield player. He has no time limits to use the ball, he can pass to a team player and different to being in his own half, he can receive a return pass without punishment.
2. Big danger for this tactic is when keeper saves the ball, he can drop kick shot into opposition unguarded net.
You make your choices, some teams use flyer gk all through game, others just when they are chasing game and clock is running down.