With my previous Ald-Ruhn mod I detailed the city a bit but when I was working on it a bit more I decided to expand the area of the city to over twice the original. A few images can be seen here http://www.fliggerty.com/phpBB3/viewtopic.php?f=23&t=6607as I said in that post I really need help if I want at least 50 percent of the new buildings to have interiors, I could just do what I did when I added more buildings to balmora but it's a bit to much to have every building say "nothing of value" in the place. I'm also considering doing all the settlements in Morrowind except Vivec City because many mods out there already make it how I like.

Maybe you should work on the interiors before adding new buildings, and plan beforehand who these houses are going to belong to. After all, there are many NPCs in Balmora (for instance) who live/work there and don't have a home -some of the Temple priests, the NPCs roaming the streets or even some of the folks at the Legion Fort nearby who maybe commute every day.

I think it would thus be more interesting, to flesh out what is already there in vanilla Morrowind, rather than to add more random content.

I'd suggest you use the Children of Morrowind mod as well, maybe throw in an orphanage near the temple.