Sadly, all indications say this won't be possible. The devs seem to want as little scripting in the game master mode as possible, and the main campaign will probably have hundreds of scripts.
You could probably recreate the main campaign as empty levels, eliminate all the scripts but use existing NPCs and stuff and then the GM could give a new personality for all the characters and completely change the feel of fort joy (e.g., add more guards and prisoners, make a bunch of voidwoken attack, etc). Not ideal, but could be fun with the right group of people and GM.
