I'll be in ADVPATH tonight till about 10:30 pm est. It's our weekly DLA meeting after that.
As for plotlines - no nothing is set in stone. But we DO need to move forward with speciifcs. I would suggest. however:
1 - the game world be generic fantasy, plug n play. By this I mean a FR/GreyHawkish/DLish std D&D high fantasy setting - the three published settings of WotC in this vein. (See notes on Eberron later)
I do agree with creating sidebars for adapting whatever it is we do to WotC published settings.
Please do remember though that most people are not going to run this as a self-contained unit. They will pick out adventures, Maps and locales, encounters, NPCs, and magic items to use and adapt for use in their own campaigns. Accordingly, those adventures which take place: in dungeon-ruins, castles, wilderness, docksides and ships - the most iconic and commonplace of D&D location based gaming will get the most use by everyone.
It is for this reason that a plotline which permits a reasonable amount of dungeon crawling is important.
2 - I think it is a big mistake to attempt to detail the game world per se. That is a never-ending battle with feature creep and will serve to alienate all the DMs of the FR/GH/DL/HF Homebrew DMs that want to use it for their world.
I think we should limit detailing areas to those the Adv Path specifcally takes place in. Focus on mapping small settlements and small towns outside of interior areas except where it cannot be avoided and we must go to a larger area.
Then put in sidebars for each of the three published std WotC High Fantasy settings. I do not mean to exclude Eberron from the FR/GH/DL triumvirate, but Eberron certainly DOES have a different feel. If there is an Eberron fan who wants to help with "adapting the adventure to Eberron" sidebars, I would be happy to do that too.