A couple of things I would like to see.
1. Instead of a braking line, a light meter or something unobtrusive on the side of the screen going from green to yellow to red. I need the braking line but I love seeing the track without the arcady line on it.
2. AI for multiplayer like PGR3. My buddy is horrible at racing but still loves to race. He won't buy forza though because he can't compete online and only two of us in the room would be incredibly boring. We play PGR3 all the time with the AI and just the two of us. DON'T MAKE THE CAR PHYSICS like PGR3, I love the sim aspect but give us AI cars in multiplayer please.
3. Better design tools and a way to sell individually created graphics on the AH not layered on a car, buy the car, highlight all the layers, rename it, yada, yada, yada
4. For tuners ability to not only put a tune on a car but immediatly with one button press buy all parts required for a saved tune. I could build cars in 5 minutes to sell instead of hours.
5. Ability to modify locked paint jobs but not resell them or copy them. If I buy a sweet paintjob I'd like to tweak it, my own number and so forth, but I shouldn't then be able to replicate. If you want to sell it you can but ALL paint is removed when you do and it goes back to stock paint. I want to prootect the painting community but if I buy a car I should be able to make some changes to it.
6. Locked tunes, locked tunes, locked tunes. I understand pulling tunes from the leaderboard, but it's to easy to just buy a well tuned car, copy the tune and the sell as your own
7. More data on the car in the info screen. How many hot laps has it run, does it have any top 100 times, top 500, top 1000
8. Can the physics be tweaked so high horsepower rockets don't dominate the leaderboards. Seems there should be more of a penatly in handeling, plus in online you have to modify your line all the time to get through corners. These beasts advantage is the straights and nobody gets in their way so they always have the advantage in online as well.
Just some suggestions I'd like to see. Love the game and play it way more then the other 40 titles I've owned.

thevilleky rocks to
http://www.bangcamaro.com