There is a huge problem building big things in stonehearth. Mutch of the problem is in the complexety of the work itself. My sugestion is to make it a feature! Making all the processing needed on a background thread and when everything is ready starts building. The progress of this processing will be at hands of one hearthling only. The architet
For example, you have that huge castle with 8 floors towers and lots of inner design. It will consume tons of resources. Hearthlings you need to figure out where all these resources are stored and if they are still there in the midle of the processing. They will need to figure out how to build on the go too, the gigant thing you made can be really unbildable (not bug unbildable, literally unbildable) like tryng to build one building inside another really big one or something crazy like that.
My plan is to have a class, the architet. When your building get too big it will only be buildable if you have the architet (a ingame figure that will represent the processing involved in calculating the solution for the problem)
The architet will first make a simulation of building having all the resources needed (this simulation dosent apear in the real game, just a thread behind the scenes). It will actually simulates building as fast as possible using the game engine, it will need to consider all the land around the plot that will be reserved. No alterations are possible to the reserved plot while the architet work and when the building starts (no mining in the area, no monsters spawning there, no destruction there, everything stays the way it is now). Player will need to put a storage somewhere with enouth space to hold building materials needed for the big construction project. Things on this storage are reserved for the big building and nothing more.
If you want to free materials you can pause your building or remove it. If re-started architet must match the old state of building of the actual to see if any plot is diferent from what was planed, if it is, the simulation must be re-made (mutch pretty like real life but mutch more cautious)
the architet is usefull preventing the gamer pc from fryng. Only an limited amout of processing will be given for the simulations required by the architet so the game will not going to brake because you tried to turn the world upside down (that is teorically almost possible in stonehearth). The architet will have a progress bar that will indicate the completion of one simulation, this progress bar can go down too (a simulation going wrong can go back to a previous alternative, like chess algoritm) Stonehearth needs a pretty good ia to calculate not the best solution (that would be impossible with tecnology now) but decents solutions. When one fails, on simulation, try another one!