They really need video footage, it will play havok, and be hilarious for a few weeks as half the league is sent off for incidents in previous games, games will be 10 minutes longer. But after the first insane month, frankly, the majority of cheating and trying to get away with things will simply stop.
THey do it now because the majority of things they all get away with it, shirt pulls, little late kicks, bad tackles trying to kick players out of games, diving, etc, etc. After a month I reckon the massive majority of those things will simply not happen, the amount of incidents that require video replay during games will dry up and most games will take just as long with video replays, as major incidents with players complaining for ages do now.
The difference would be fair games, for all teams, all the time, with no exceptions. Even the worst ref would get 99.9% of decisions right with video replay.
Of course referee's salarys would have to increase to compensate for their loss of a huge secondary income
Utd and Liverpool might even be able to pay off some debt with the extra money aswell.