I honestly think the 4th official should have a monitor that he can view incidents on. I think it will help with reducing the amount of diving, shirt pulling and commotion inside the box. If a player knows full well it can be reviewed on camera by the official they will think twice before doing it.
A system similar to American football could work well, each team has a limited number of 'appeals' that the captain or manager can use to appeal a decision and have it reviewed by the 4th official.
As for the argument of it taking time, stopping the flow of play or the like. It would take 2~ minutes for the 4th official to review an incident and walkie talkie it to the ref. The time taken can be added at the end as extra time. The flow of play is already broken when players surround the referee and have an argument with each other.