I only played Driver a bit so I'm not entirely sure I know what I'm talking about...
However, If this would give you the ability to rewind/fast forward, that would be incredible.
What I would *love* to see is... Anyone remember the original Need For Speed for the 3DO (it wasn't as obvious/useful for the PS1). When it did the replay, it didn't save the entire race, it saved what it considered to the be "highlights" of a race... Now, in NFS, a highlight was driving between 2 cars or flipping your car 8+ times in the air, however, it was a great feature.
The reason I'd love this is, I spend a ton of time playing friends on GT3. It is horrid that I have to sit through 4 laps of adequate (boring) racing to see on the fifth lap where one of us pulled the race out of the fire to win it all.