After catching up with everything here is my current plan.
1. Fix the current Underdark Saga so the boss fight at the end works. If I can't get it to work I'm simply going to remove it as I'm sick of screwing with it and who the heck is going to really play Oblivion once Skyrim comes out? Not me.
Quite a lot of people who--leaving aside the issues associated with endorsing features still in flux--simply don't have the rigs to handle Skyrim properly, and don't want a buggy game that will lack a lot of great mods for at least a year. Yours will likely be one of those exceptions, but as someone who watched this mod community from the start, I saw just how long that took to get going.
Outside the endless and early series of leveling/scaling mod fixes, of course.
But I am delighted you're doing some fixes to Viconia. It remains the most extensive quest-oriented companion mod in Oblivion, and in my opinion, the best. Thanks for all your work, and may you enjoy your time under Skyrim's sun.