are you talking about sectioning off a part of a world and wiping it and then remaking all the terrain with a new biome or seed?
What is wrong with that? A better solution may exist if you explain the purpose of it. If you are talking about some sort of worldedit, you would save all blocks into an array, or if you are talking about how to reset an arena after playing a certain minigame, same thing as above may apply, but it would be better if you just disabled auto-save and unload the world. Also, it is not clear on whether you want a new world to have a part preserved or you want an original world to rollback before certain changes are applied.
