- A flyable jet, like the lears at the Airport.
- An attack helicopter/airplane. (like the Apache in ALL HANDS ON DECK, or an F-16 that fires missiles)
- Residental neighborhoods.
- The ability to steal things from businesses/homes.
- The ability to sell things.
- The ability to buy/steal things to customize a vehicle/place.
- Mini-Games (like the annoying arcade game in the Taxi garage...but playable)
- Legitimate car/boat/aircraft dealership.
- Character customization.
- Variable destination Taxis.
- More control over your gang.
- Diplomacy with other NPCs (Police Chief/Mayor/Other gang leader/etc.) A cellphone would be a good interface for this.
- Swimming.
- Gambling.
- Many more Interior spaces.
- Neighboring small cities/towns that can be visited.
- More control over business assets.
- Better police AI. (Why surrender, it dosen't get you anything?)
- Diffrent military services.
- Better pedestrian/driver AI.
- Ability to attach trailers to certain vehicles. (Boat trailer, car trailer, plane stairs at escobar, etc.)
- More realistic carnage.
- Higher detailed people models.
- A brothel, lol.
-More, I'm sure, but that's all I have for now.