While I'm trying to keep as close to actual game play as possible, I did end up taking a few artistic liberties in my story. One such liberty was finding a Gate Master in Harmondale; in the game, it cannot be done, but in my story I decided to have it so that one approached my party in town, looking for work.
Another liberty I took was the party's background --- in my story, they're all lifelong friends from New Sorpigal. Thus, I do have a few nods to MM6 in this one...and the group's being from halfway around the world also helped me come up with a small dispute among the four shortly after arriving at their ruined castle.
It's definitely a little more time consuming than I'd anticipated, but it's slowly coming along. When it's complete, I'll let you all know.