I'd like to see fully adjustable real time day to night transitions as well. I don't see how that's all that hard to pull off in a racing game. Action/adventure games have been doing it convincingly for nearly a decade. Not so sure about inclement weather conditions, though. If it's not hard to implement realistically, then sure. But I have a feeling it's alot more work to get that to work than it seems.....and it's not something I'd want Turn 10 to spend a whole year working on when they could be working on something more worthwhile. Regardless, I would like to see dynamic track conditions that actually affect car driveability (ambient temps, track temps, wind conditions...).
I also agree on more smoke. They need a better particle effects engine altogether. Forza 1 had more dust and smoke effects than 3. I'd like to see that get corrected if possible.
"Wise man say: Forgiveness is divine, but never pay full price for late pizza."