Technically the harvester is already able to move at an destructible(ore) instead of going random point around an region (albeit it cannot identify whether the said destructible is alive or dead). The circle of power may be tricky to do since I aimed the refineries to be buildable so I cant rely with Region Event and probably need to think more about it. The stacking items could be interesting for the replacement of mana though.
Here's the demo.
Here's the demo.
You could create a circle of power for each refinery where the harvester unloads the spice. The ore could be collected as stacking items in the harvester's inventory so it won't have to stick to a specific same place to harvest. Of course, this mechanic has to be triggered and the units and their actions indexed.