I know people hate the idea of sin bins, but yellow and red cards are really poor tools to manage a game with. Yellows are really meaningless on the whole, yes players might be more careful but when you know the next time you give a yellow its a sending off it can't be easy for refs. Having sin bin cards instead of yellows (they could still stack up for bans over a period), and red cards for actual violence and maybe deliberate actions like hand ball on the line. This gives the ref far more control over the game as if someone is a twat and makes a shit tackle they're off for 5 mins, do it again and its now 10 mins etc. Works in other sports would work in football.