IceX 3.0 is a world editor for Gamestudio from Oliver2s, but not yet ready to go. Conitec themselves are writing a new official Leveleditor for Gamestudio. And Sivan is creating an advanced world editor that seems to be very powerful. http://mapbuilder.zxq.net/

I personally would recommend to use Blender and import the Levels into MED and then WED.