I liked that quite a bit but theres one thing I have to question about that.
You'd need a ton of missions to occupy all that space.
Heres my Map:
Size: 2x of San Andreas
City #1: A city similar to Liberty City which is really dark and seems bigger than it really is. I also think it should start of with you being in the gutter with nothing. Name: New Clifton (I dont know if this is a real place I hope none of them are)
City #2: A paradise for holidays, its built on a desert and its a theme similar to Vice City. There are hundreds of night clubs like the Malibu here. There is a Mafia expanding across this city. Name: Marina City
City #3: This is a suburban paradise similar to Shoreside Vale, this is occupied by two main gangs, The Rollers and The Blue Kings. There is mostly gang control across this city and constant gang wars taking place here. Name: Victoria City
City #5: A very freindly town, the only problem is the drunks at night, there are so many pubs and clubs here that its only natural that many poeple start throwing molotovs and start fighting eachother here. Name: Orchard Acres
Countryside: There is a desert nere Marina City which is occupied by a few poeple in trailers who will try to stealth kill you if you come to near to their property. There is a large Canyon here also which you must get through to get to Victoria City. Name: Gash Canyon.
Between New Clifton and Marina City is a large feild type area full of freindly farmers but also a few psycho's. There are many strangers out at night willing to kill you because you there. Name: Ruby Feilds
Between the other cities is mostly hills and mountains like Mount Chiliad, there are mostly warm weathers but there is many winds and tornado's here.
You can go into any building and they are all unique in one way. Some are inhabited by poeple who will give you advice, but most of them will tell you to piss off.
Many of the buildings can have something to do for you like Banks, which you can rob or store money in. Houses which you can buy or rent. Apartments which you can live or rent out. Properties, Gang Houses and much more.
Car shops to have a car spawn outside any of your houses.
(Enough ranting im bored)