Maybe we should adopt the card rules from soccer or the five foul threshold from basketball. Technical fouls even. But ejecting only defenders is grossly an exaggeration.
Simple two card system is maybe too limited. The idea is to make it a team penalty that migrates to an individual penalty. How about 3 colors: green, yellow, red. Green card is used to warn a player to behave after an aggressive or a non-deliberate violent act, and there is no immediate punishment except leaving the field for the next immediate play AND having to don a green jersey for the rest of the game. A yellow card is for a second green card violation by the same player and they are lost for the remaining quarter. Yellow cards would also be instant for major penalties by a player. Make the yellow card offenders don a yellow jersey for the rest of the game. And the red cards would be instant ejections with a dead ball field goal try by the opponent from the 40. Any subsequent red card leads to a field goal by the opponent from 10 yards closer.
But anything other than the current system.
I hope this is a joke.