To me, Vice City only really worked because of the 80's setting. I'd like to see a new city based of Detroit, Chicago, or maybe Memphis-focused on gangs. Carcer city would work too.
Not arguing your point but woukld like to add a couple of other notes about VC.
Florida is a delta and flat as a board meaning no mountains or even hills.
I think what made VC so cool was the feeling of being in another era. Thes could easilybe done with the 1960s or 70s in any other city. I have an itch saying "SF & LV" which would work nicely. Hippies and lounge lizards anyone?
You guys act like you cant recreate the feeling.....And Miami isn't just a beach guys, nor is it a "sandy city". The beach is literally on a seperate island to the east with the west being a swamp... The only areas with sunshine and fake palm trees are Miami beach (an island) and downtown... the rest is Iraq....
To answer OP, I really truly want a Morden day rendition of Vice City but a city that artistically and ego-wise is stuck in the 80's. Either have a story about a Cuban immigrant with a Niko-esque story or a Jewish retiree caught between a rock and a hard place.
Keep everything modern day Miami, just change all the buildings, art, cars and clothing colors into exaggerated pastels and neons (even make the Pay'n'Spray colors pastels only). Have NPC's fashion choice inspired by 80's trends yet still modern day apparel, same for the protags clothes. Have that "always party mode" atmosphere to the city, kind of like the TBoGT vibe. Lots of drug themes. Lots and lots of drug themes...
Don't forget to throw in some 80's rendition cars alongside the modern ones, the Miami Vice undercover cops that show up at 4-stars, and for god's sake don't forget the VICE CITY FM!!!!