I'll echo the chorus of "These are some good quest ideas." One thing I did notice, though: You mentioned adding more content for Paladins . . . and then (write smaller) for LG Fighters and Priests of Helm as well. Personally, I feel the game is already slanted
enough towards Good without anyone increasing the tilt, so I was gratified to see you exploring the Fallen Paladins angle as well.
Re: Class- and Kit-specific material: In general, I think it's a good way of helping to keep one game distinct from the next, though of course one can go too far. One has to marry credibility (e.g., a true-class Monk or Druid would not be offered a counting-house as their Stronghold) with players' ease of seeing the new content, to find a happy medium. So, I say you should go ahead and make the main quests class-specific (those who don't like it already have Multi-Strongholds installed anyway), and make the subquests
marginally kit-specific: Those not of that kit can still take that quest, but a) only by having to navigate a more complex conversation tree, b) only if they have the right stats for it, and/or c) only by giving up another quest so they can do this one instead.
And what's this about the Paladin and Cleric strongholds being the shortest and dumbest? Haven't you guys ever played a Druid?