Punish ALL offences in the box that would warrant a free kick on the pitch with a penalty. No holding, blocking off,clothes lining or pushing , John Terry's career would be over in a week. There would be chaos in the form of sendings off and penalties until the players learn what is unacceptable.....could be great fun !
I heard an interview with former referee Graham Poll a few weeks back about this very thing. He said that no offence occurs until the ball is actually in play. I'll admit I didn't appreciate that. He went onto say to give a penalty the ref needs to watch the corner being taken and the players at the same time, not easy. To give a penalty the ref would have to be absolutely certain that the defender committed the first offence, again not easy if you're also watching the corner being taken. He did say that the best defenders time their release of the shirt/player at the time the corner is taken to perfection and quite often attackers get penalised because they don't. In Dunk's case he was probably very naïve by continuing to pull Keane's shirt up his back after the corner was taken, he should have let go sooner & Keane would have probably pulled him over.