I generally don't think illegal defense types of rules are great for the game, as they seem sort of fake. But, the NFL has changed the rules so much to favor the passing game that when the passing numbers go down, the overall product looks really rough. No one wants to watch a guy drop back 30 times to throw short routes that go no where. So some rule changes that encourage big plays and rushing the ball would be great. Not particularly sure what those would look like, but I think overall it would make the NFL more interesting to watch.