Before I begin, the keyword is REALISM!
Imagine this (some of these ideas are inspired by other games) :
A city, a real or fake one...doesn't matter. But it HAS to have the following:
1: streets that would be a common race hotspot
2: Countrysides/mountain passes
3: Highways
4: Pedestrians
5: Police
The clock is realtime, say it was noon at wherever you're at, it's noon in the game. And in the day, there's no racing of any kind. It COULD be possible, but the chances of getting arrested are HUGE! So instead you do jobs, like deliver pizza or what not.
But once it's night....Then the action begins. People cruise around town, looking for challenges, it could be a 1/4 mile race, a circuit race, a uphill/downhill race, and a wangan race.
Say you feel like racing Initial D style. You can drive up to the mountain passes for some touge action. And the following things happen:
1: You look through your friends on Xbox live to see who is online, and challenge them to a race.
2: Maybe it's the hotspot for tonight and you want to meet a new face, win some money, anything!
3: Practice! Maybe you're experimenting with your car and want it tuned to the right balance for a touge race.
Then comes 1/4 miles:
You show up at a gasoline station, a parking lot, a street, or just cruising! some punk is talking trash through your headset? Maybe you want to make some money? or you simply want to race?
Talk to the person you want to race, find a hotspot and race!
The 2 of you can line up, and BOOM! you're off. But it has to be real, you can race pass intersections, but chances are you will get into an accident...or a cop sees you. Or a report of a street race will be filed.
Wangan:
probably the most dangerous and risky race. You have to have a seriously tuned car for these! Driving 200+ MPH avoiding traffic. It's all about reaching point A to point B without getting arrested, losing, or getting in a wreck. These types of races should NOT happen constantly since I don't think people would want to see 50+ cars racing along a highway, realism is key.
Circuit Race:
The safest, legal race available in the game. You have your 1/4 mile race which will also be the official time keeper to see who has the fastest car, or you can chose a circuit for some lap racing since you've tuned your car for circuit races. Up to 25 cars can compete in lap races. These form of races are reserved spots. First come, first serve. Entry fees do apply to compete in these races.
Now comes the realism part of the game:
Weather: weather should play a part, fog at the mountain passes/countrysides, raining on the Wangan....it all should affect you. Sometimes it can pose as a threat.
Traffic: It should alter during the hours of the day. Midnight-5:30, not a soul in sight (if you're on the touge). Maybe a few cars here and there. 10:30-5 PM. Rush Hour traffic. Also let's not forget those holidays! tons of cars are on the city streets and highways, maybe a slight more cars than usual on the touge.
Police: You should be given the option to be either a racer or a cop. But there is a catch: You can't speed! just cruise, watch out for illegal racing. Once you hear a report, or see it...it's so on right now. With your headset, you can notify other officers (that are online players) that a race is going on. You can also pose as an undercover cop to bust races, or pilot a helicopter.
Risk Factor: I don't see CONSTANT races everywhere. There should be a meter depending on your location on how likely cops will come to that area. For example, say you've been racing at this one location everynight and someone has either filed a report about it or there has been alot of busts, then cop players are gonna wanna patrol that area. So you either go to another spot, or wait till that meter goes down to race another time. And in order for that to happen, you gotta lay off the racing.
Tuning: I vision tuning as detailed as you would see in games like Gran Turismo and Forza Motorsport. Anything is possible to be done with your car, inside and out.
Driving Physics: Again, real and detailed. Every car behaves differently with the real aftermarket parts and bodykits.
Cars: hundreds, ranging from Tuners, Muscles, Exotics, Bikes...
Money: Let's be real now, do we want to see people ALL drive Bugatti's? Ferrari's? NO!!! Money should be earned in real life!
Damage: If your car is damage, it should affect the performance, it can be repaired...or it will be be crushed if you don't do anything to it.
This is pretty much all I can think of, what do you think? In simple terms, whatever goes on in the Street Racing world...should be in this game.