One major problem of current duel gameplay is that for player who manages to get item control the game is too relaxed. He doesn't have to doo much, it's always the other player who has to think of something to turn the game around.
Solution: damageable/destructable powerups. Shoot a rocket at MH, and it doesn't give full 100 hp anymore. Do enough damage and you destroy it entirely. Now it's not enough just to time items, you have to make sure you get them fresh and undamaged or not destroyed completely. You have to control not just items, but also the opponent, to not let him destroy your powerups. On the other hand, if you're out of control, now it's easier to switch it, by damaging your opponent's stack before he gets it.
This will also make gameplay less limited. Player's won't be anymore forced to play under "I have control, therefore I win" dogma, it will open new ways to gain a victory.
If you have or have not any comments, please discuss.