This is my Fallout 4 idea.
Location: It should be based in Russia and one highly irradiated place could be Chernobyl. There should also be a big city like new vegas and you can pass through Chernobyl to get there faster or you could go around it for a more safer way to get through.
Factions: The Soviet Union (Neutral) They should have red armor with the Soviet symbol on the chest and they should be good and Melee and guns, the leader should also have a war hammer and sickle wielded or glued together and they have accesses to vertibirds.
I'm not sure what to name this faction but they should be about Democracy and the leader should have Blue, white and red power armor with an eagle on the chest.
Enclave (Bad) They should be communist type enclave and you can get them to ally The soviet Union.
Raiders (Bad) Just normal raiders but you can join them.
People like NCR but with a different name, they could also have accesses to vertibirds and they are at war with the Soviet Union.
Companions: A Russian Super mutant called Vladimir he will want to join the Soviet Union but not the NCR guys. He should be found in Chernobyl.
A dog like Dog meat but you can name him. He can be found at a dump.
A ghole who is captured by the Raiders. he can be found in there main base. You can buy him for 3000 Caps, if your speech is at 70 you can get him out for free, if your batter is at level 50 you can buy him for 100 caps, you can break him out but the Raiders will turn hostile.
A mister gusty called P.E.T.E that you can find and Repair somewhere in the big city.
That's all I can think of right now but I'll probably update this.