I’d be designing a map that would cater to my ideal roleplay experience. I know what I want the best. DarkRP doesn’t fit that, as it is something I’d hardly consider roleplay. Entity wise, any mode just needs spawnpoints and doors. Most modes were built around existing maps.
First, I’d select a theme that’d be unique and interesting, something that’d stand out. I’d want this place to be memorable.
Second, I’d put on my urban planner hat. How do people live in this city, what locations and functions do they need? Government provides management and utilities: law enforcement, fire protection, justice system, healthcare, education, power generation, water pumping, waste management, transportation administration, and public spaces. Residential is where people live, housing, apartments, condos, mansions, homeless shelters, RVs, under the bridge: you get the idea. Commercial involves everything from selling goods to services, flea markets, bars, spas, offices, and banks. Industrial you get dirty industry, manufacturing, high tech, and agriculture. Then you’ve got all your transit: how do people and goods move around? Cars, trucks, pedestrians, boats, airplanes, bikes, busses, trains, etc. and what facilities support these? Then you’ve got the crime: usually these guys adapt to their environment, but they can get some love too. Moving around out of public eye, out of the way places to hide people and operations, places to dispose of goods and people, casinos, etc.