Hello can someone make mod like this one? it allows to farm nether warth oustide nether http://www.minecraftforum.net/topic/906002-110-blocker226s-minecraft-mods/
This one "should" be fairly easy. If I recall, you can plant netherwart in the overworld, but it won't grow. A plugin that implements the scheduler to do a periodic random chance to update the block data to the next phase (perhaps in an area around a sign or some other marker?) should work.