Im not saying that all this list should be in GT5 but almost half of it can be done.
01- Faster on the curbs and smarter AI;
02- Day -> Night transitions and Weather effects like rain, blizzard, etc;
03- All famous real circuits and city courses (F1, DTM, Endurance, Drag Strips, etc.);
04- No more special cars!;
05- More detailed physics (tire pressure and temperature, brake temperature, etc.);
06- Damage system (not visual, just like the one in Sport Car GT, just a degradation in performance), and pay to fix the mess you did;
07- More information of the car like the use of replays to create graphs of the lap that shows tire pressure (inside, middle, outside), Suspension travel, fuel consumption, etc;
08- Damage of parts of the car due to wrong settings (a car too low can damage the bottom of the car and the tires because of bumps in the track);
09- Races with full grid just like in real life;
10- A better field of cars to race against, more limits to the cars that can enter in the race, HP, Tire, etc. but specify this limits, not just sport tires but N1..N3, S1..S3, etc;
11- A Calendar based set of races were the races have a date in the year to appear;
12- A time and usage scale to the parts of the car, like blowing a engine for overheating or over revving or mileage, buy tires regularly because of wear (no more infinite tires), replace the suspension, form time to time, etc.
13- I'd like to see more F1 models old and new, Indy, Nascar, drag, etc;
14- A minimum of 10 Laps in big circuits, 15..20 in small ones and 2 or 3 in Nurburgring (no more 2 lap races!);
15- Customizable difficulty settings for AI speed, aggressiveness, etc. (like in the Nascar games);
16- Determinate the fuel load before the race;
17- The use of real units in the car setting;
18- Use of a real fuel unit and each car having its tank capacity
19- A real working dyno (like the one in NFSU2);
20- External modifications depending to the parts that you add, like half of big twin turbos coming out of the hood, or the big blowers of a supercharged engine;
21- Adjust the dimensions of the wheels of the car independently (Front/Rear), Id like to put smaller wheels in the front of a old muscle car;
22- See the adjustments in real time and the function to simulate bumps to test the suspension travel like in LFS;
23- A wheel that not only have 900o of rotation but a clutch and a shifter (like the act-labs RS shifter);
24- Be able to repaint the car after you buy the car;
25- Cockpit view with Dials, gauges, lights, windshields that get dirty and switches to turn on/off the external lights;
26- Car detailed information and history;
27- Rally courses not circuits and rally courses should be more open;
28- Back with the wheel collection from GT3;
29- Dynamic track temperature during the day and/or night racing;
30- More control over the replays, fast forward, rewind, stop, slow motion. Just use the soccer games replays as a example;
31- Full screen replays in the 2 player battles and the choice to add as many AI cars as you can.
32- Skid marks and leave some of the colorful paint of your car in the walls and other protections on the track;
33- In arcade a option to create a race where you chose the cars youre going to race, the track, the weather and if its day or night.
34- Every race in GT mode, single or championship, should have a practice option and a qualify option.
35- Qualify and practice should be limited based on time or laps <- better;
36- The option in GT mode to choose your car from a list before you enter in that race;
37- Sponsors in GT Mode to help you out with the expenses, and add the logos in your car.
38- The ability to save in the middle of the race, for the endurance races;
39- The cars should have different needs and costs, like the time to change the oil and the price;
40- More aerodynamic enhancements and the ability to customize them. Change the height of the rear spoilers and visual aerodynamic enhancements in the front of the car;
41- A more complete physics engine where the car can flip and do burnouts and doughnuts.
and
blu3s
Better Sell Values
- If you sell a car with so many miles on it you get less/more cash than the same car with more/less miles. Or you could get more for selling cars with upgrades.
Enhanced Lightweight/Aerodynamic Modifications.
- The ability to pick what lightweight mods you do. Carbon Fibre bonnets, boot lids, ect... as well as professional aero kits. Im not talking like.. the Steet Fighter custom kit for yer honda civic, im talking real race worthy C-west and the likes brand aero kits. You know the ones that provide an actual purpose.