TheProlificPenTheif

A lot of dunmer lore and cultural concepts were built around two main cultural philosophies, honor and ancestor worship, the second of which is the primary focal point within their entire cultural-religious design. Much of their culture, from core beliefs, architecture, and even the design of their weapons and armor are heavily based upon specific elements of japanese culture. Many japanese natives practice various forms of ancestor worship, and honor in life to attain a good standing in the afterlife is one of their top priorities. In this situation, most, if not all, dunmer would consider it a dishonor not to be bound to their ancestral tombs. They would want to be able to protect the future generations of their clans, houses, and bloodlines, borderlined obsessed with securing their place in their family history. Perhaps even going so far as to soultrap themselves to items, a legendary warrior might soultrap themselves to their sword so that the next generation of their family will literally be able to use them to slay their enemies. A skilled wizard might bind their soul to an exquisite robe of persuasion to help their children and grandchildren be better suited to attain their goals diplomatically. And so on. Any dunmer in good standing, or of a well established house, would basically consider it treason, or sacrilegious to rob from the dead, much less slaughter the ancestral guardians of dunmer tombs. The dunmer even take great care when handling the dead of other races, almost never defiling the resting places of others. They just take it to a religious level. Basically, any proper dunmer, poor or rich, would want to kill you with their bare hands for so much as entering a tomb you didn't have the bloodright to do so.

I've never had the pleasure of playing a Morrowind Mod in my life, a disgrace I'll be changing very soon, but I do have over a decade of experience playing unmodded Morrowind. While I'm woefully unprepared to help you locate the mod your looking for, I can tell you that your looking for a mod as there are no "mannequins" of any kind in the base game nor the expansions. Sorry for the lack of otherwise useful help.