Moveable Mob Spawners Using Nether Stars

Combining a mob spawner and a nether star should make the mob spawner a breakable block that players can collect. Then the players could place a limited number of spawners (4-6 seems like a good range for the maximum) in the same area

Mob spawners are very fun and useful, but often player-made spawners are more effective, and with a good reason: if mob spawners were able to be moved, this would create a huge imbalance, especially when players are in the early stages of a world. However, some players would rather use more natural methods of "farming" than creating massive airborne structures that drop mobs from the sky, or other such projects. 

Moving the spawners would be a nice addition if something could be done to balance it. Requiring a nether star to move a spawner means that it would be impossible early in a new world. Even late in the game killing the wither is no small task. You could also limit the number of spawners that can function in a certain area, to ensure that players aren't given too great an advantage.