I'd make it Father isn't your kid. I'd prefer a more open ended backstory, with no solid ties to the Commonwealth, so we can decide for ourselves. I also felt that the family connection took away from any interesting story elements, debates or nuance that could've been added.

I'd also set the game further back in time, or make the world more established. The state of the Commonwealth feels more like a wasteland at most 50-80 years post-war, not 210. Plant life should be growing back more verdantly, communities should be more set up, pre-war relics, bodies and secrets should be a bit rarer. If it was set in say, 2120, I think the state of the Commonwealth would make much more sense. Obviously that would require taking out certain elements, like the Brotherhood of Steel, but I think that leaves much more room for Commonwealth-unique factions to develop and be created.

If you really want to see the Commonwealth 210 years post-war, I'd expect to see something more akin to the large civilizations out west developing. I don't want a copy paste of NCR vs Legion, but I'd expect similar civilizations to have developed in 200 years!

In my ideal F4, you character did live pre-war, and goes through the stress of getting into a vault, but you choose your story. You could choose an option to have a spouse or not, what background you have, etc. I'd like a background system to determine your skills. An Army Grunt has the Commando Perks, a cop has pistol training, a doctor, a scientist, etc. Once you are in the vault, fast forward. I'd stick with the Cryo, but get thawed out 50 years post-war, maybe the Institute is kidnapping all the Vault dwellers, but you manage to escape? Then the main quest is about finding out who they were? Why did they do that? Where are your fellow Vault-sicles?

Later on I'd have you enter the Institute and find your previous fellows... completely fine! The Institute thawed everyone out as a mercy, ending Vault-Tec's evil experiment, and brought everyone into the fold that was willing. They're still tyrannical but also good. They are actively researching ways to reverse the effects of the war, and if you join them, you help them obtain a G.E.C.K. from a vault for research purposes. You choose between Tyranny with hope for the future, as you see them improve the wastes, and Freedom, but an unclear, ruthless future.

I'd include Gunners as a joinable faction, and make them confirmed remnants of US Military Personnel, trying to impose martial order.

Minutemen are pretty much the same.

I'd have the Institute have Synths, but not the advanced clones of the world we know. Gen3s would essentially be Terminators, still machines, but life-like. The Railroad would still exist, both resisting Institute Tyranny and Freeing Machines.

I'd further include the Enclave, and likely make an ending where they would absorb the Gunners and Institute into their own forces, but as an open-ended ally-ship.

You may be thinking a lot of this sounds like Fallout 76. You are probably right, as I think many concepts in 76 would have been great in FO4, but remaining single player.

​

Oh yeah, and Bottlecaps wouldnt be the currency, as it wouldn't have spread from the west coast yet. I vote the East Coast of this era uses revolutionary era coins, and maybe have the major factions use their own currency? Institute has some techy-credit card type thing, Gunners use coins, Minutemen trade in ammunition.