But how do you fairly stop the game to make challenge? How quickly does the challenge have to be made?
How do you fairly restart the game if the challenge fails?
What stops using a challenge to break up a counter attack late in the game?
It's a minefield.
It's not, start with limits
- you can question goals/penalty decisions - game has stopped anyway
- you can question red/yellow card calls - as above, game has stopped anyway
If you just added that to goal line technology you would have a better game than today.