I'd like to see an MMOFPS of a combination of A Tale in the Desert, Minecraft, and Planetside
You start the game at the edge of the wilderness as a blank slate with no attachments. You're given a blank diary, a pistol with five rounds, and a sleeping bag. From there, you do as you please. If you die, you have to make a new character. The only exception to this if you've built a medical building which gives you a supply of lives. Upgrade the building for more lives.
You can store weapons and supplies in bases or warehouses which you also have the build. Otherwise you just carry everything on your back. You can build garages for vehicles, and bunkers for defense. You can build and lay traps such as landmines, or dig trenches and fox holes.
You can join groups. The only groups are ones made by players. Leaving is easy. Joining is easy. There's nothing to mark that you're in a group except what the group decides to mark them as. This could be a tabard if you want. People can fake these tabards though to fool other people. The benefits of groups is the sharing of buildings. Groups can form alliances. Friendly fire is never on, and you're never told upon death the name of the person who killed you.
The world is divided into territories. To control a territory, you have to be the only one with buildings in that region. Otherwise it's contested. Control them all, and the game restarts with a newly generated world. The location of resources would be determined by seeds. The conquerors aren't rewarded. Conquering the world isn't the point. If you want to spend the entire game putting landmines on a road and watching from the distance through binoculars, you can. If you want to travel the world as a mercenary or engineer selling their services, you can.
Your diary records yours and other people's experiences. You can collect other people's diaries by sharing or just killing them and taking it. Through this, the history of the world is written. For ease in cataloging, when 10 or more players from two or more groups fight, it's considered a skirmish. Three skirmishes equal a battle. Three or more battles equal a war. These are recorded. The names of the dead are recorded. As are the completion of buildings and historic discoveries.
No NPCs, no grand story to drive you along, minimal backstory. The small amount of backstory would be told through the game's environments. Abandoned cities in ruins, mass graves, radiation, and craters. These would be recorded in your diary when you find them.
Basically, the entire game encourages players to be a dick. Killing other players, sabotaging their stuff, creating anarchy isn't just encouraged, it's rewarded. You have to constantly balance your ambitions with those of other players. You have to consider who you can and can't trust.