I was sorting through my Data folder and I found an almost-finished WIP that's been kicking around on my hard drive for almost 3 years! I think it's finished, save for the rooms/multibounds in Castle Volkihar. You know that thing where you just get a wall of fog because the rooms and portals aren't set up/linked properly? That's my issue - it looks like you're stepping out into thin air, you take a pace forward, and you're in a room. I tried hard again, today, to line up the portals but I just can't get the hang of it.
Could someone PM me with their email address and I'll send them the file? I think, once that's sorted, the file will be ready to go.
Thanks
Princess
Screenies: http://s43.photobucket.com/user/princess_stomper/library/Clean%20Dawnguard%20Castles
The mod: It just dusts off the cobwebs and rubble, adds a few potted plants etc. and some more sleeping areas for player/companions