Unit based vs. Map based Interaction
Whenever I am playing such games as Victoria, Europa Universalis or Civilization, I sometimes feel myself being overwhelmed when having to deal with the dozens of units sprawling the map. Especially when you finally have reached the status of a large sprawling empire and the game is nearing its end. Though it is lovely to see your army approaching a million men, but it just clogs up the whole map. Not to mention the workers, navy and rebellions (barbarians) that clog up the map. To new players this sight might sometimes be overwhelming (I know, have tried to get my friend to play Grand Strategy.. not a big success). Luckily in all of these games you a actually manage this mass of units. Why? Because the game has a pause button. So all is good. Sadly, that won't work for a perpetual open world.
However, what is you suddenly start playing this game with other people and you have to work together with lets say 4 other people. Not only can't the game be paused, but now suddenly you have 4 times the units you have to take notice of and maybe even direct yourself. A scenario like this would just leave the player incapable of functioning, especially against an AI, which in many aspects has the intelligence of a dead-beat monkey, mind my french.
I could go even further my adding that the units have their own perks and stats, strengths and weaknesses and other stuff the developer adds to make, what are essentially the same unit, more interesting for the player. What I am trying to say is that having so many individual units under your control might not be the best thing when you want to represent a strategy game, especially when you want to make it a multiplayer. What will happen is that you make the game less accessible to the player. You want to have something in the sense of plug-and-play. Where the player doesn't need to spend 5-10 minutes reviewing what he did right before he logged out. I mean hell, the game is going to include a lot of automation, and thus worsening the problem.
Now then. What I am going to propose if nothing short of utter blasphemy. What if, what if, what if... we got rid of unit based interaction? Now don't misunderstand what I am trying to say. I am not trying to say that we should create a press button to attack country A> Press another button to make peace with country B, etc. No, no, no! Quite the opposite. All I ask is to not have tanks the size of mountains bombard the city with shells that take up entire living quarters in size. No. What I instead want is thousands of troops marching on the battlefield, and see them lay waste to everything that crosses their path. Is that so much to ask? I think not.
Consequently, this would require us to move from a unit based system to that of a map based system. So instead of sending workers like you would have in Civilization to create a farm next to a river tile you would instead allocate resources and manpower, and you would see the farms developing and get bigger the longer you have your focus on that area. Discovering the area around your city is not a question of moving your scout to tile x and y, but rather you organize a expedition or have your hunters seek for new hunting grounds. Which would then be seen as scouts setting up camps with plumes of smoke reaching above the canopy. As you with Far Cry 3 when trying to find outposts, but then from a bird-eye view.
This might all be very hard to imagine, as personally I have yet to play a game that abandoned all the idea of units. However, even if we kept the idea of units, we could still do some pretty amazing things with the map when it comes to warfare. Instead of having a bunch of units you would have a large standing army defending the contours of your borders. You as a general can then influence the tide of war, which would then resemble something more in the shape of a wave or area of influence. As a result the aspects of war is integrated into the map and stuff like terrain would have a much bigger impact. Giving you the possibility to go Sun Tzu on someone's ass.
This would take the 'tactics' out of 'strategy.' What I'm guessing is instead of a panzer group that you micro, you have the 8th panzer division move as a whole and roll/stat against whatever. Hopefully you don't scale up to field armies, but the concept remains that large armed units remove 'outmaneuver' and turn it into 'outproduce.' At least taking this at purely face value. How would the blitz of the Maginot been successful if Germany had made a beeline over it?
Several grand strategy game implement this, so I assume in this concept units have a variety of stats to rock-paper-scissors each other. Maybe the Germans will have an 'maneuverability' rating, or an attached general will have an ingenuity rating, which balances against a toggle of fortifications having '0.' But this may require micro that your concept is looking to avoid.
In what way would it take the tactics our of strategy? Because currently any of the games in the Grand Strategy / 4X genre is more about stacking units and letting them run into each other, or having a huge technological advantage and slaughtering thousands with an army of two.
Lets say we have such a thing as Civilization 5, where you have a unit that can move in different directions (well 6 really). He's quite limited in the area he can cover, but if you compare it to say tile-based combat, then what could happen is that you own x% of that tile. And you moving your army with the use of, for now, lets call them factors you might gain the strategical upper-hand by driving your opponent into a corner or trap him between your crossfire. Not to mention the idea of reinforcements would have a much bigger impact. Same goes for terrain, like rivers, as you'll have to position your wave of troops in such a way that it is not easily defeated. Like you can hold an important river crossing and not have to worry about them crossing it 2 kilometers up-stream.
How can a larger maneuverability be bad for tactics? You'd still have stats and perks, but they would define your army of platoon as a whole.
Widen the scope of your thinking here
So... Don't get rid of units, but find creative ways to hide them or indicate troop density. Such would be the case with a probabilistic agent model. Just like in reality, the leader of a country doesn't direct where every tank ever goes; but not every person is going to be a leader of a country.
That though changes depending on the type of game engine you build on top of the base simulation layer.
So imagine a game that is primarily a version of "Civ" with players in control of a culture or nation each. (Much easier to do with a post-Westaphalian-treaty nation-state model). Anyway; since the whole planet is mostly agent based, generals and commanders will do whatever the hell they want. If your culture supports a strong central authoritarian state (created procedural) then you will get to have the supreme leader exert larger control over individual actions.
But the main point is that control is there if you want it and automatic if you don't because you literally have an AI or a model of AIs that makes its own decisions based on your guidance. Pick your followers closely.
I have more but have to run. Cheers!