This is for a setting I'm slowly building up for my own writing / game creation needs. We used this setting as a background for (a sadly very short-lived) RPG campaign before and I was pleasantly surprised over how many good ideas the group came up with after just a cursory explanation of the culture, so I figured this place would be great for even more useful ideas.
First, some things about the setting:
The world: A fantasy world with a past apocalyptic event of uncertain nature. Each culture has a different and (even internally) conflicting version of what happened. All that is for sure is that there was a golden age, bad stuff happened, old gods were abandoned and new ones rose up to stave off apocalypse. Race-wise (mostly?) humans, but magical and weird creatures exist.
Nature of undeath: Undeath in this setting is built around the idea that living, animate things require three things: a cognition, a body and animating force. Undeath at its simplest is "just" replacing one or more of the three with varying means. For example, animating a corpse with magic and using it like a puppet, rather than creating an autonomous creature.
Practice of necromancy: The necromancy used by this culture focuses on separate preservation of both soul and body. Souls are trapped into gemstones fittingly called "soulstones", while bodies are preserved, possibly through methods similar to embalming. A soul is transferred from body to body by implanting the stone in a prepared area in the body. All of this is governed by laws and practiced solely by religious authorities. Both the bodies and soulstones require regular maintenance to preserve. All services are rendered for a price.
Flaws: Necromancy is always flawed in one way or the another in this setting: in case of soul binding the soul retains the personality, skills, beliefs etc. of the soul in question, but is very slow to change. As such soulbound ancestors are bad adapting to the changing world.
Ancestors: Ancestors are revered in this culture, but where a more mundane culture might worship them, this culture opts preserves them. Each family considers it a matter of honor to maintain a shrine for the ancestors, allowing the descendants to converse with their ancestors for guidance. The costs, however, mean that one's place among the ancestors needs to be earned. Ancestor may, at any time, decide to leave the shrine, although this tends to be seen as ghastly omen for the family if done for no reason --- or even more so if the reason is something the family has done.
The culture: Feudal society with heavy emphasis on family relations and especially ancestors. Think something akin to (early) medieval China. Emperor at the top, noble families below them, lesser families below them and so on. The emperor is an ancient ancestor who died without any heirs centuries ago, but still retains all power over the nation. His court consists of both the living and the undead.
Applications of necromancy: Beyond enshrining ancestors, there are other applications in this culture for necromancy: labor and warfare. Bodies suited for these purposes are preserved for use, while living warriors aspire for the honor of adding their souls to those of the ""immortal legion". Peasants on contrast sell their souls to decades of labor to enable their families to afford to maintain the shrines to their ancestor(s), bound to fitting body after death to keep repaying their loans in full.
Restrictions on necromancy: Since the form of necromancy used here requires a soul to control the reanimated body, souls strictly need to be cooperative ones. Similarly, bodies used are preferred to be at least nominally adapted to the work they're intended for. As such, there is very little incentive for enslaving souls of enemies and maimed bodies are worthless. The souls of the native population are coerced to honor their obligations by shifting the burden of debt to next-of-kin if a soul proves uncooperative.
So, as per the title: What kind of industries would legal and regulated necromancy spawn and require?
For example: I would imagine gemstones of the kind that are used for the soulbinding would require whole industry dedicated to procuring and preparing them.