Would have kept Wigan up and sank Sunderland! Would not have helped Man City though, even if they did win, but they would have won the FA Cup.
How about an extra point for ever team that win a cup game, but this would not be good as it would not be the league and the luck of the draw could see someone like Spurs get Arsenal and go out and us go all the way getting lower league sides. It could also see the gap for the top teams get even bigger at the top, rather than closing the gap.