I discovered this thread just a few days ago. I haven't tried editing planets yet, but I can't get the method for creating new solar systems to work. I start a FF game, go into WorldBuilder, find a spot for a new solar system (sometimes clearing nebula or radiation clouds to make room), save map, exit BTS, restart BTS and FF, start scenario using that map as a scenario. The game locks up when it tries to load that map as scenario.
I'm using BTS ver 3.17. I've made only two file alterations - the CIV4ArtDefines_Feature.xml fix for the WorldBuilder terrain edit buttons, and the CheatCode edit in CivilizationIV.ini.