These are the MOST requested features for Gran Turismo 8 according to Reddit.
I tallied up all the comments to give me the top 5 to share with you guys.
Time stamps below :)

0:00 - Intro
0:29 - Dirt Build Up
1:17 - Qualifying and Grid Starts
2:23 - Multi-Class Racing
3:57 - Improved AI
5:29 - Cosmetic Damage
6:13 - Related Content