Hello, EMC! I got a little bored today, so I downloaded the most recent version of MC Edit, and I made the nether into the overworld. I turned netherrack into grass/dirt, I turned fire into roses (Poppies), I turned red mushrooms into dandelions (Flowers), I turned soul sand into sand, and I turned lava into water. If you'd like to play on this map and explore a little, there's a download link here: http://tinyurl.com/q64y6yu
Well, it is just the Nether with edited blocks. I wasn't sure if there was a way to change the biomes.
Sure thing. Here's the version with stone: http://tinyurl.com/kd7bz5w Here's the version without stone: http://tinyurl.com/q64y6yu