This would be my main concern with it (i.e. that it ends up not solving much at all). The laws of the game are so vague that most incidents can be argued either way. We see this every week with players, managers, pundits, fans and even qualified referees all disagreeing with each other over the same incident.
The clearcut, 100% certain fouls are relatively few and far between, and while I agree it's imperative that something is done to make sure those decisions are right, the majority of the time we'd just be introducing yet another layer of subjectivity that's open to abuse.
The problem lies in the laws of the game, something that isn't such an issue in the likes of tennis, cricket and rugby.
just like rugby if there's doubt you don't give it, but go through the process, to not do it is negligent in my eyes, there is so much at stake at the top level of football, yesterdays was so blatant and obvious it was ridiculous