In a nutshell why Miami is an iconic city for GTA and why it is a must:
According to the U.S. Census Bureau, Miami's metro area is the eighth most populous and fourth-largest urban area in the United States, with a population of around 5.5 million.[8][9]
Miami is a major center and a leader in finance, commerce, culture, media, entertainment, the arts, tourism and international trade.[10][11] In 2010, Miami was classified as an Alpha- World City in the World Cities Study Group’s inventory.[12] In 2010, Miami ranked seventh in the United States in terms of finance, commerce, culture, entertainment, fashion, education, and other sectors. It ranked thirty-third among global cities.[13] In 2008, Forbes magazine ranked Miami "America's Cleanest City", for its year-round good air quality, vast green spaces, clean drinking water, clean streets and city-wide recycling programs.[14] According to a 2009 UBS study of 73 world cities, Miami was ranked as the richest city in the United States, and the world's fifth-richest city in terms of purchasing power.[15] Miami is nicknamed the "Capital of Latin America",[1] is the second-largest U.S. city (after El Paso, Texas) with a Spanish-speaking majority, and the largest city with a Cuban-American plurality.[16] "
and the city itself, Florida is just flat land with little elevation changes. If they can't work fictional islands into it the game would get stale quickly, especially with Mafia III coming out set in New Orleans, which is also a lot of flat land, but that will get here first.

