Just a few ideas.
1) A bowling powerplay which lasts 5 overs, and instead of the field being in, the batsmen aren't allowed to hit the ball. Therefore, if you can get 10 hits of the stumps in 30 balls, you should take this powerplay immediately, and you might just bowl the team out for 0. Batting team gets to fiddle with their order, obviously, so you won't be able to get the best remaining batsmen out every time unless you are accurate enough.
2) Three sets of stumps. The batsman can't defend them all. Run up as if you're going to bowl to one set, and then change it up at the last second and have a crack at another set. Will really test bowlers' accuracy, as an agile batsman could only cover two sets at best.
3) One hand one bounce.
4) All fielders get gloves, to increase the chances of catches.
5) If the ball hits the batsman anywhere other than the bat, it's adjudged LBW. Occasionally, if it's a bad shot, it might be LBW anyway.