Hi! I would like to join to your project as level/interior designer. Here is an example of my work: Adventurer's Asylum. It's my first mod, but I hope, that I'have been able to avoid the most common mistakes such dirty edits, GMST, etc.
About your showcase requiremnts:
1) It's actually even bigger
2-3) As I see, this requirements checks the ability to adjust items on the non-horisontal surface and not just press "f". There are pretty much examples of such object placing in my mod. For example, weapon on the table in the cellar.
4) 166 objects for the first cell and 232 for the second one
5) Yes, for both interiors.
6)10 lights for main cell and 30for cellar. Water level is configured cellar only, for obvious reason. It's a player house, so I didn't forbid player to sleep there :)
7) Yes, it's my own work.
About using unique/quest items: there are two of them, actually, and they are not so unique:
Chronicles of Nchuleft - this one could be bought in the regular book stores
Boethiah's Pillow Book - yes, the original game contains only one copy of the book. But when player brings the book to Aengoth, he asks player about where s/he has found the copy. So Aengoth doesn't think, that there is only one unique such book in Morrowind :)
About mixing styles, a little Introduction about the previous owner of the building:
The previous master of the house was a dunmer adventurer. He was very interested in ancient history. Especially he was interested in Six House and Dwemers. And his library clearly demonstrates his interest. He even brought to his house a few pieces of Dwarwen furniture and clutter from Dwemer ruins. Among them is the Dwarwen Alchemy Collector, which is the most useful of his findings. Actually, I just wanted to make a house with scripted storage for alchemist, but I hadn't discovered another way to explain this device :) So I had to create this character. He was quite well educated, but he wasn't an academic scholar (he even allowed himself to read during meals). He trained with his weapon regulary, but he might relax with skooma too. He walked the whole island, but found his death in the Dwemer ruins near his home... So, using of Dwemer&Ashlend clutter isn't a mistake :) I did it for the purpose.
Dependencies: Morrowind.esm (obvious) and both Tribunal.esm and Bloodmoon.esm for their ingredients.
Fitting the exterior: it's OK, I think.