Hello there.
I came up with this f** crazy idea that I have never ever seen implemented in any game: regame a replay
Maybe my english not strong enough to explain the idea but, I know "Test drive" option exists in single game/hotlap replays since the replay contains all details from setups, so you can drive the car with same setups.
I wonder if this could be implemented on a multiplayer replay. You'll start always last and you'll race other cars that are predefined on replay, they will follow the path they did on the replay and they'll be invulnerable. You'll be able to race yourself or others, try to enjoy the race you liked from another point of view. Check if you could have done better, etc
Obviously since it is a replay, cars will not be able to defend themselves while you are overtaking.

edit: I enjoy watching replays from years ago, when I used to race on leagues, that's why I came up with the idea

You mean racing a ghost from a replay? Like in Colin McRae rally 03-04 and etc. as like trying to improve yourself while you race yourself? I think it was possible, but I may be wrong.

It sure was. In the older versions.

https://www.lfs.net/archive

Well, not exactly a ghost from a replay. It is not possible to get drag from a ghost.
A replay does not record every detail it happened. I think it records the position, speed and direction, then the game simulates with physics what should happen and matches pretty well with what actually happened.
I can conclude that since on "single player" races you can edit your replay and add objects. Then you'll see that cars will crash/interact with objects and change the prerecorded behaviour. Sadly the replay will return an error and stop playing since it did not match with what is recorded.
I think in previous versions you could do the same with "multiplayer" replays. Therefore, it leds me to think it could be 100% possible to "test drive" (add yourself last to the grid) and play.
That way you'll enjoy the replay from inside, taking part on it.
For example "could I take part on the world series?" >> Play the last race of an LFS world championship and check if you could keep the pace fromt he inside

It's a cool idea, but without some crazy AI machine learning algorithms, it can not be done. If you want to interact with cars whose actions were pre-recorded, what happens when you crash into them, will they keep driving the same as if there was no crash? Even if they do, for sure eventually it will lead to a crash?

On the other hand, racing ghosts from a replay is very reasonable and can be done.

Suggested it some time ago: https://www.lfs.net/forum/thread/91829

AFAIK some CS:GO analysis software works like that, you put yourself onto the map in the demo, so that you can practice tactical setups, etc. Can't remember the name of the thing, but 100% it exists.

EDIT: ESEA Refrag is the name

Quote from Ziomek21 :

Suggested it some time ago: https://www.lfs.net/forum/thread/91829

AFAIK some CS:GO analysis software works like that, you put yourself onto the map in the demo, so that you can practice tactical setups, etc. Can't remember the name of the thing, but 100% it exists.

EDIT: ESEA Refrag is the name

Cool.
I considered the idea so weird that I did not check if other threads were open, my bad.
So yeah, some other people agree with your idea,

This is definitely a cool idea. It should be added

turns out it's used in football training too, although it looks a bit... funny

Do you mean something like this? It follows "checkpoints" with some corrections that have been recorded previously (could be recorded in replay also).