Interesting point about goalkeepers, though. There's obviously a timer on the 10 minute sin-bin. Once that 10 minutes is up, there has to be a decision about what happens with the goalkeepers. If they simply swap with the player already in goal and someone shoots or crosses the ball, requiring goalkeeper intervention, there could be great confusion at the swap-over. The only realistic way to do it is when there's a break in play and the returning keeper can get themselves set and ready again.