if Grand Theft Auto VI were to have a single city it would have to be Vice City. Las Venturas and San Fierro would be great as well, but i feel they would be too similar to Los Santos. (City with wooldand area and desert). Vice City is based off of Miami, FL, therefore it could have a gulf coast area, thick as all hell swamps, plus the city itself.
Now We know that R* would like to have multiple cities. the question is, how would the mechanic work?
would it just wilderness/ small towns like SA? or would be a transfer system like your garage follows you around?
I would hope for the former because R* has proven time and time again they know how to make a beautiful countryside.
if we go with the former and add multiple cites, which ones do we use?
I would vote for Vice City, San Fierro, and Las Venturas. these 3 cities are the only ones that haven't been used in the HD universe.
As for story, how do we build it around the world we create?
well I would think we start out with a protagonist a con person (maybe a lady?) making a living scamming and stealing in Las Venturas. maybe they come upon a rare commodity (perhaps the cursed diamonds from GTAIV?) what should've been a standard job goes south, the protagonist is wronged and/or stolen from. and they embark on a "cross country chase to get back the one who wronged them (sort of like Foxy Brown). this protagonist chases the wrong doer to San Fierro. Here we meet Protagonist No. 2 (If R* wants to keep the multi-protagonist mechic) And older man (i'm picturing Steve McQeen/Clint Eastwood type) who works as a wheel-man, a smuggler if you will. He spends his time getting rare illegal, stuff in and out of the city. Protagonist 1 meets Protagonist 2 a number of times but they don't really like each other. if at all. only when the cops get involved do they actually agree to work together.
-this opens up the opportunity for Heists (because i think we can agree those where some of the best missions in GTAV)
during one heist, the antagonist shows up causing the whole thing to go down the crapper.
the Wheel man manages to get them both to a safe house back In Venturas. one there they do some searching around to find out where Antagonist has gone.
-bare in mind there would tons of side-missions between all this,
Switch to Protagonist 3. in Vice City a low-ranking mafia errand-boy who finally gets prove himself on a job. unfortunately this job is being set up. by the Antogonist and it goes wrong. The boy's the only surviovor, the entire Mafia gets sent after him forcing him to flee to Las Venturas where he meets Protag. 1 and Protag. 2. The Unlikely trio now know where this big bad is and opt to go after him, upon arriving in Vice City they have to power through lesser mafia families, crooked cops, and the like before finally having a showdown with the antagonist either atop a skyscraper or a massive Mansion (though i fear the latter would be too similar to VC)
That's the gist of things. of course there would be plenty of side-quests and minor missions here and there.
I for one think they should keep the setting in modern times but i think there's definitely room for a 70's themed story DLC like TaD or TBoGT.