Meh, I would prefer just to have a fallout game filled with zones like the first two fallouts. (that way there could be more people in the areas and more actual content per zone) I really don't need an open world at all. I actually get annoyed even with Fallouts New Vegas which liked when I'm walking/running around for a while I just felt like I should be doing something else meanwhile like walking around in the real world, lol. I also HATE vehicles, just about always. I didn't get Fallout New Vegas because it was open world though, I got it because it was a Fallout game made by Obsidian. I think it is a good game if one thinks of it as an RPG and not as an open world game. Or I like good RPG games that may fail on some open world aspects because I'm the type of loser that wants to not be himself, lol.
I hate to say this, but I think open world would work best if it had some kind of way to use the kinect or some kind of wii remote. I mean, think of how many miles even with using fast travel people walked in these open world games, (also riding a horse I think can be pretty strenuous exercise actually). I personally would like a system that allows me to walk around a fantasy world or sci fi world with my own body. I think it would be a fun way to get some actual exercise. (I'm not joking at all here... believe it or not)
I also HATE when people just call Fallout New Vegas an expansion pack or DLC or whatever. I hate fucking DLC because it makes people think OMG something has the same graphic engine and uses the same textures it has to be DLC!!!!11 I wonder if back in the 90s did people who played games make the same complain when a sequel used the same graphics such as Fallout 2, the king's quest games, etc. I much rather have more content, and the game using the same textures if it saves time and money that could be used for the rest of the game.