Zombie Swarm Intelligence
It's hard making smart zombies. Not only is making smart things hard, but there also just isn't a lot of room in the spell matrix to put thinky bits in. But, as one drunken apprentice once pointed out, while there's not a lot of thinky bits in one zombie spell, in a lot of zombie spells there's more room. What if they could talk to each other?
So that's what this spell-design is meant to do. It takes what we have learned from the Basic intelligent design and then redesigns the zombie-spell work to go massively parallel with its brainz, allowing all zombies in an area to share their reasoning ability to problem solve, navigate, tell apart friends, foes, and people wearing badly fashioned masks, figure out tool use, and master the exotic secrets of the doorknob. With all of them working together, a zombie swarm should be... well, bright is a strong word. But no longer brain dead. (If not literally. Zombie brains are still dead brains. They just don't act like in any more. Assuming the project works.)
Floating Skulls
It is a fact that, of all necromancer apprentices, only around one in five, or one in ten depending on whom you talk to, survive to become a full fledged necromancer. Over the many many years this city has been in existence, this has lead to truly large amounts of dead apprentices. Now, they shall be reused. Even if they failed, an Apprentice Necromancer's use of magic has still infused their corpse with an affinity towards necromantic magic, making their bodies easier to work with and enchant then some random dead peasant. This applies to both their flesh and, more usefully in this instance, their bones.
More specifically, it also applies to their skulls.
These skulls can, with the proper runes carved upon them, and given the proper necromantic treatments, be infused with fragments of their former possessors will, giving them some, if minor, will and initiative of their own, while also easily being used as a conduct for any true necromancer whom is attuned to them. This leads to a magic floating skull, smart enough to follow, or skulk, around targets without needing supervision, from which the attuned necromancer can either look out through their empty eyesockets, or project their voice through to give orders and otherwise command any local undead troops. Or just to talk to each other over long distances, depending on where the magic floating skull in question is.
Granted, the skull is basically useless for combat, but between the uses in spying on the enemy (either by having it skulk around and follow enemy troops or just putting the skull on some high tower for a birds eye view of the city whenever the necromancer needs one), commanding troops without actually putting a necromancer's own highly trained rear end in table, and gossip... er, communicating and coordinating with ones peers at long distances, most people think it is useful enough as is.
Bonesmith
It is a fact that our current source of worked metal is, well, pretty shit. Fortunately that is easily fixable. First off, we get our blacksmiths modern tools of which, and this is the true stroke of genius, we actually bother to maintain and repair when they need it instead of insisting that the blacksmiths in question 'do more with less'. Secondly, we add zombies. Yes, I know zombies are idiots. But they're idiots whom are very good at doing the same thing over and over again, which means they are a natural at tasks like 'pumping the bellows at a certain rate' and 'moving heavy blocks of unworked ore around' and 'hitting something with a hammer over and over again'. This lets us shove off a lot of the boring work on the undead, while the living only have to do the bits that require actual brains and attention. Hopefully, this will work to solve our metal income issues.
Wheel-Lift Quarry
It is a fact that our current quarries have certain sharp limitations to how deep they can get, because at the end of the day you have to actually be able to get the stone out of the Quarry and that means the ramps can only be so steep, and that means that to get past a certain depth the Quarry has to be unimaginably large. So let's stop using ramps all together, and instead we'll put a giant wheel powered lift in to lift blocks of stone out and lower workers into the pit. And we'll power the wheel that powers the lift by putting a bunch of zombies in the lift and ordering them to start running when it needs to go up or done. Should work just perfectly.
Tower of the Dead
As is, our Moratoriums are small, and therefor only can ready a small amount of corpses every day for our use. The simplest way to fix that is to just make them bigger. Instead of some small basic building, we'll devote a whole tower to the purpose of getting the dead bodies ready, and with a whole tower to work with, we'll have room to specialize buildings for certain forms of undead. These rooms for basic zombies, those ones for higher quality dead bodies to turn into iron zombies, dead Dire Vultures up on the top rooms where they can fly out, Bonebreakers in that big room on the ground floor with the double doors so they can actually exit the building without bringing down a wall, and so on. Oh, and with more room, it should also let us work with some more 'special' corpses, instead of just human bodies. That would be useful, right?
Banefire Distillery
While the Necromantic brewer works, one can not deny it is a simplistic, and most of all slow, solution to a problem all Necromancers have. One solution to this is to build a big, and proper, Distillery for the purposes of making Necrotic fluid, powered and heated by great bone fed tanks of banefire which melt down all that flesh and those secret herbs and spices in a jiffy, instead of depending upon wood fires and big cauldrons to do the work. Really, it's long past time to modernize and industrialize some of these old methods, wouldn't you think? It also gives us a ready source of Banefire for... other purposes. Should we ever find ourselves in need of evil life devouring flame, I mean.