Movable blocks via mine cart.

Not only would this be a neat way to implement a way to make moving builds but it would also give minecarts more of a purpose. How cool would it be if you could build a train that actually moved! You could be able to place blocks directly on top of a minecart and when the minecart moves those blocks on to move with it. Therefore if you had enough minecarts and a big enough track you could build a moving house or a slightly odd-looking train. I feel this idea implements essentially vehicles without ruining the uniqueness of how Minecraft implements things.