I think it would be a nice addition to the Biome Crystal use to be able to craft a sort of wand that can change the biome in a spot/range when used. It could have unlimited/limited use, configurable.

What do you think?

That's what i'm currently working on for the next update :). There will be a Biome Collector that will collect biome essence which you can then use to change the biome somewhere else.

@lumien231 Will you fix fertilized dirt changing to regular dirt after placing a sapling problem? :)