[attackdrone]

Mines and Farms are already in as Earth/Nature sites, but the hardcoded limit of four sites per provinces makes it unwieldy to add universal unlockable sites such as roads.

Immobile easily summonable units that give benefits could be more workable, such as:


Construct Earth Blood Mine
Requires Construction 5, Earth 4, 30 Earth Gems
Summons an "Earth Blood Mine" unit which is immobile, has no attacks, and generates 2 Earth Gems per turn. (Unit has no slots)
Can only be summoned in Mountains or Border Mountains.

Construct Floating Refinery
Requires Construction 7, Air 4, 30 Air Gems
Summons a "Floating Refinery" unit which is immobile, has no attacks, and generates 2 Air Gems per turn. (Unit has no slots)
Can be summoned in any terrain.

Establish Astral Research Academy
Requires Thaumaturgy 7, Astral 4, 60 Astral Diamonds
Summons an "Astral Research Academy" unit which is immobile, has no attacks, and adds to Magic scales. (Unit has no slots).

Establish Court of Justice (Multiple Versions)
Requires Construction 0, Fire/Earth/etc 1, 10 gems
Summons a "Court of Justice" unit which is immobile, has no attacks, and reduces unrest. (Unit has no slots).

Erect Grand Temple of Sacrifices
Requires Blood Research 7, Blood 4, 80 Blood Slaves, Unique Spell for Blood Nations
Summons a "Grand Temple of Sacrifices" unit which is immobile, has no attacks, reduces population slightly, causes unrest, but spreads dominion like a Prophet. (Unit has no slots).


Obviously these are not balanced, and are just raw ideas, but might be workable.