A game where you play a faceless mook against a well-armed, smart shooter protagonist.
Story is, you're a soldier in the Evil Empire. Okay, you may be essentially working for a hellish combination of Nazi Germany and the Soviet Union, but the pay is good, they make the trains run on time, and you need to feed your family. You agree that The Good Rebellion is morally in the right, but the state is still recovering from the massive war against the Evil Empire and a revolution would really screw things up. Get to work, soldier.
Gameplay goes like this. The game has a Papers Please like family that you have to feed between levels, and you get paid depending on what you do in the game. You start out as a lowly Private, ordered to guard a fuel depot or something that would be the setting of the first mission of a regular shooter. You have a mass-produced rifle that is horribly inaccurate, a manual that barely explains anything and is mostly useless propaganda ("Shoot enemies of the empire! Gain victory! Gain money! Gain trust of the empire! Begin rejoicing!"), and a coat that can only keep out the cold. You have a set list of areas to patrol and check for enemies of the state. The maps should be fairly open-ended, and have plenty of little details so that it doesn't get too mind-numbing. However, after a while, the hero would arrive. You are fighting against the protagonist of some other shooter. Their AI should be highly advanced and their equipment really good. They have a set of objectives that they must complete. They range in terms of character: sometimes they are sneaky sorts, other times they are cold-blooded snipers, other times they like explosives. There should be various traits involved with them: for example, sometimes they prefer to do the minimal amount of killing, other times they slaughter everyone.
There are various ways of dealing with them. You can attempt to take them on mano-a-mano, but that's going to result with you getting killed nine times out of ten because as said, your rifle is terrible and they are very skilled. You can wait for your squadmates to wear him down and get killed, followed by you finishing the job, but if they kill him first you won't get the bonus payment for dispatching him personally. You can attempt to run away and hide in a cupboard, but this will definitely get your pay docked and they will hunt for you if they like slaughtering everyone.
As you manage to survive against the onslaught of heroes, you get promoted. As you go up and up, you get better weapons (Guns that don't jam half the time and don't aim to the right! How is this possible?), the option to command your subordinates (Go over there and die for the Empire! Me? I'll be right behind you!), and better armor (You can stand up to the enemy with the chance of not getting immediately killed!). Storywise, the situation is getting worse. The Good Rebellion is growing in power, and the Evil Empire is losing more supporters by the day. Slowly but surely, you go on the offense. Of course, this means you're pitted against enemies that were as useless as you were at the start (The friendly AI in shooters can be pretty bad), so this is actually a release in tension.
However, things get rapidly worse as you become a target for the enemy at your high rank. Heroes begin to target you personally, making the levels suddenly much harder. At this point in the story, the Evil Empire begins to lose. After a few missions that get more and more desperate, going from "Blow up the bridges allowing the Good Rebellion into the capital!", then "Defend the tanks firing at the Good Rebellion's infantry!", to the penultimate mission being "Retreat to the Palace, the Evil Emperor has a plan and it will work, honest". The last mission takes place at the palace with you as the sole survivor of your unit. The Evil Emperor approaches you and congratulates you for your service to the Empire, then he knocks you out with a pistolwhip. When you wake up, you see him in civilian clothes running to an awaiting helicopter, finding you in the Emperor's clothes. Then the ultimate hero of the rebellion kicks down the door and gives you a witty one liner that would be pretty cool if you weren't in the villain's shoes, quite literally. So begins the hardest fight in the game.
If you manage to lose, then the game's end is set to triumphant music, describing the great new democracy that has risen from the ashes of the Evil Empire, showing pictures of the Evil Emperor (You) being spat upon by his gravediggers as he's buried in an unmarked grave, and finally noting that this victory is not without sacrifices (Showing your family sitting on a street in rags next to a cardboard sign saying "NO HOME 4 CHILDREN PLEASE GIVE $$$"). Essentially, everything you worked for in the game has been destroyed, but the world essentially got better.
If you manage to win, then game's end is set to ominous music, describing the way you managed to take control, destroy the last of the Good Rebellion, and ultimately rule with an iron fist (Not actually specifying if this is a benevolent or evil rule), then finally showing a picture of you and your family all smiling (For the first time in the game) and holding each other. Essentially, the world is now under the rule of a possibly cruel dictator, but your family and you got out of the game on top. It's ultimately your choice which ending is the happiest one.
I think this would be a great way to point out the weirdness of FPS games by introducing an outside prospective. I think the recent wave of FPS games pointing out the oddities of themselves is a good direction, but doing it from the POV of a regular FPS protagonist doesn't work as well as doing it from another perspective could. Also, this should be preferably done without going the Overlord-style "You're pretty bad but your enemies are much worse" route. The Good Rebellion are as the name implies, good. The Evil Empire are utter bastards and deserve to be kicked out, but the problem is that you are just trying to provide for your family yet you are an equal target, which from your perspective puts the Good Rebellion firmly in the wrong.