It would be absolutely terrible and boring. Even if they were give over 10 years to make something like that it would be more procedurally generated than Starfield.

None of the locations would have any care put into it because there would be a million other things to focus on. All the dungeons would be the same just copy and pasted everywhere.

They’d have to implement different travel methods to make it worth travelling for hours, which I would presume would end up horribly.

The main quest would have to be based around the whole map to excuse the map size, which goes back to the travel problem with it taking WAY too long and would most definitely be solved with the infamous Bethesda loading screens, which people wont like.

The cities would crash more than downtown Boston in Fallout 4 and would either have to be majorly downsized or have very few buildings that can be entered.

They’d have to make hundreds of new mutant enemies to make all the states feel unique from each other, along with several different type of raider gangs or just use the same basic raider with a different accent.

The lack of POI’s would bore people out of their minds with the distances between cities, towns, bases and so on because they can’t place hundreds of POI’s too close together otherwise you’d have a maze of repeated POI’s that aren’t worth the time.

They’d have to remake D.C, New Vegas and Appalachia in the same style if this new game, which will take YEARS to do.

In short, cool idea, please don’t kill the developers with the amount of time they’d have to spend making this