Ok, so you know how in game replays, people who are replaying the game can switch between the line of sight of the various sides and see what each side sees?
And in a normal game, if you see an enemy unit with your structures, you know he has probably seen you.
Anyways, I was thinking how cool it would be if you could have an overlay that recorded and summarized that information that the player already naturally has about what the enemy has or has not seen.
Anyways, what does this overlay look like? Well, if a unit is in the vision range of an enemy unit that is in YOUR vision range, they get an exclamation mark over their head. If a structure acquires an exclamation mark, it will keep a small semi transparent mark to notify the player that the enemy has scouted the structure. On mouseover, it shows a timer of when you last scouted. When you mouseover an enemy structure you have scouted, you also get to see a timer of when it was last scouted.
So, this overlay would ONLY be available to people if you also opened yourself to risk. What is that risk? You have to construct a building. This could be called a great library, a map hut. anything you want. The point is that if you build this structure, you gain the overlay while the structure is available… but you also open yourself up to a massive amount of intelligence risk. What is an intelligence risk? Well, what happens if an enemy saboteur or spy or agent were to sneak inside and burn your maps that you had stored inside the intelligence structure? Your map becomes unexplored.
Anyways, this intelligence structure can build spies. Spies have no attack, low health, and can be killed by pretty much anything. Even workers. But, spies can climb over walls, and if a spy melee attacks an enemy intelligence structure, the structure burns, and the enemy loses all their vision. They have to reexplore the map. The spy is an infantry unit and can garrison rams. So you have to be extra vigilant about enemy rams if you decide to build an intel structure.
The thing is, if your a professional aoe2 player, you already are able to manually track what the enemy has or has not seen in your head. If a single enemy red dot appears on your minimap, you magically know what unit it is, the vision range it has, and if it has or has not seen your buildings and units. You don’t actually need this overlay.
However, for the rest of us, we could use a crutch to see how many minutes ago we saw each structure and the time the enemy scouted our structures. But, if we use that crutch, the professional player can counter our use of the crutch with this interesting spy minigame. The nice thing about this is that if you ignore this mechanic entirely, and your good enough, it wont have any impact on the game outcome. But if you don’t ignore this, then it might actually end up losing you the game even though it gave you temporary advantages. And ofc if your a semi professional, you can delete the intel structure if you suspect a spy might be on the way 
