It would be good if we could record again the replays, but this time we're controlling the camera, and make some pretty nice videos (It would be some kind of director mode).
At the very least, bring back the single screan VS. replays. The split screen thing just ruined one of the best parts of the game. Also, hopefully with the PS3's abilities, they'll let us up load our favorite tunes as a soundtrack... that goes for regular racing as well.