[Endoperez]

I disagree with this idea for two reasons. First, there is no need to separate the school of construction from other magic by making construction require another building. If there are siege engines, there is no need to make them require anything but a fort.
Secondly, I don't agree with your view of the buildings of Dominions. Let's talk about Temples first. For Pangaea, a forest glade is enough for a temple. Late Age Marignon might have temples such as what you described, or perhaps MA Ermor. I doubt most nations even have cemeteries in or near their temples, because temples don't make dead bodies disappear any faster except for LA Ermor, in which case those dead bodies come alive faster.

Similarly, some nations might have need for such a complex laboratory - but a Mictlan laboratory would be very different. Machakan laboratory wouldn't be anything even close to that. Ulmish lab would be like the Forge you described.

You list things that could happen in a laboratory, and expect that any one of those things could happen in every laboratory at any one time. In reality, however, most nations won't have good dungeons for blood slaves, master alchemists will be almost unheard of (300 gp!), torture or autopsy or charnal rooms would only be used by some nations and mages...

Laboratory costs almost half of the cost of many forts (1000 gold seems to be the most common fort price). We don't know what goes in there, but in my opinion, it could be a Covenant.

From Ars Magica 4th edition rulebook (the system that impressed Dominions magic system, concept of gems, mages, perhaps even the way path and school are separated):

A covenant, most basically, is a place where a group of magi live together. It might be in a manor, a castle, a ship, or a hole in the ground. Covenants provide for the needs of magi in several ways. First of all, they provide security. Mythic Europe is a dangerous place for all, and magi in particular need safety to perform their arcane studies.
Covenants also provide for the mundane needs of magi: food, clothing, work space, and the like. Most magi would prefer not to have to devote their time to such concerns. Finally, covenants provide magi with a community of peers. When in a covenant, a magus is surrounded by others who think about things in the same way that he does.
Covenants are also the most meaningful way the members of different houses work together and learn from one another. Although some covenants are composed only of members from one house, at least two thirds are composed of magi of different traditions. In fact, loyalty to one's
covenant is often the strongest loyalty a magus feels, even
more than loyalty to his house.

Different Houses could be interpreted as more than just national mages: Witches, Amazons, Sorceresses, or at least Druids or Shamans of the various tribes. Covenants of Ars Magica include the mages themselves, their Companions (bards, Captains of the Guard, rogues and scoundrels that the mages have befriended, Arthur Pendragons and other characters who are important, but not to the same extent as someone who could fully tap to the primal forces of magic) and a horde of Grogs (servants, smiths, hunters, masons, woodcutters, bookbinders, leatherworkers and everyone else needed to keep a community alive) who don't need a distinct personality (but could be given one).

A covenant in Ars Magica is designed to have everything the mage needs, except for the spesific spell that must be researched or the Vis (gems) that must be collected or traded for from outside the Covenant. Sagas (adventures and campaigns) could center around supplying the covenant with what it needs and perhaps protecting it from mobs or infernal forces. In my opinion, a Laboratory in Dominion can hold everything a mage will ever need, from servants to forges to complex devices to a storage room full of glass vials.