The last ten minutes of games would degenerate into a morass of challenges and substitutions. 5th ref is perfect. The question is whether he has veto power over the ref, or acts as an advisor. I think 'chip in the ball' style technology would be about as effective as having a video ref, more expensive, and much less useful. So I'd rather they introduced a video ref straight away. The orange card idea is needlessly complicated, but I would have a rugby union style clock (that stops when the ball goes out of play), to cut out timewasting. Also it's obvious to everyone that clear diving and incorrectly judged dangerous play should be punished after the game.