Bukkit

What is the enhancement in mind? How should it look and feel?
Instead of bouncing a player back or TPing the player to the other side of the world, map two worlds together so that if the player crosses the boarder in one world they enter the other world at the same point but entering it. The effect to the player is the two worlds would equal one spherical world.

The effect could be even more effective if both world boards are oceans only thus providing an almost seamless transition between worlds.

Sending a player to the spawn point of another world once the border was reached would be most useful.

Combined with Multiverse and Monster Apocalypse one could create a series of progressively more difficult worlds with the challenge being to reach the edge of each world.

This would make an effective ladder style game.